After talks with PM Shinzo Abe, President Barack Obama has reaffirmed his support for Japan in its row over islands with China.
Barack Obama, who is on a four-nation Asia tour, warned against escalation in the dispute and said he wanted to see the row resolved peacefully.
He confirmed that the islands fell under a security treaty that commits the US to act if Japan is attacked.
Barack Obama and Shinzo Abe also discussed a major trade deal as well as North Korea.
The US president arrived in Japan late on Wednesday ahead of stops in South Korea, Malaysia and the Philippines.
He is not going to Beijing but relations with China are expected to dominate his meetings with regional leaders.
After talks with PM Shinzo Abe, President Barack Obama has reaffirmed his support for Japan in its row over islands with China
Barack Obama’s trip – which ends on April 29 – comes nearly seven months after he cancelled a visit to the region because of a US government shutdown.
Officials say it is aimed at reassuring America’s Asian allies of its commitment to the region amid concern over China’s growing power.
On Wednesday Barack Obama had an informal dinner with Shinzo Abe. The two leaders then held talks on Thursday morning and gave a joint press conference.
“Article five [of the US-Japan security treaty] covers all territories under Japan’s administration including [the] Senkaku islands,” Barack Obama said, echoing comments published in Wednesday’s Yomiuri newspaper.
“We do not believe that they should be subject to change unilaterally.”
“This is not a new position. This is a consistent one,” he said.
However, Barack Obama also said he told Shinzo Abe that it “would be a profound mistake to continue to see escalation around this issue instead of dialogue”.
The islands are called Senkaku in Japan and Diaoyu in China.
Japan controls the islands but China has been strongly pressing its claim in recent months, flying and sailing vessels in and out of what Japan says are its waters and airspace.
Japan depends on the US for its security, under a decades-old alliance that dates back to the end of World War Two. If Japan is attacked, the US is obliged to come to its aid.
China’s foreign ministry said on Wednesday that it opposed the US stance.
“The so-called US-Japan alliance is a bilateral arrangement from the Cold War and ought not to harm China’s territorial sovereignty and reasonable rights,” spokesman Qin Gang said in Beijing.
Shinzo Abe and Barack Obama also discussed the Trans-Pacific Partnership, a giant trade deal involving 12 nations.
It is currently stalled partly due to a row between the US and Japan over agricultural tariffs.
North Korea was also on the agenda. Barack Obama wants Tokyo and Seoul to work together on the issue, but ties between the two remain badly strained because of war-related historical issues.
Barack Obama flies to Seoul after Tokyo, amid reports of increased activity at Pyongyang’s nuclear test site – potentially suggesting a fourth nuclear test could be imminent.
A Chinese navy vessel harasses a Philippine supply boat off a disputed South China Sea island, in a spat witnessed by Western journalists on board.
Journalists on board of the Philippine ship have witnessed Chinese coast guard vessels trying to block access to a disputed shoal in the South China Sea.
One of the Chinese ships radioed to demand the crew turn around, or “take full responsibility” for their actions.
But the Philippine boat, ferrying food to troops stationed on the Second Thomas Shoal, managed to slip past.
The shoal is one of many flashpoints in the area, where several countries have overlapping territorial claims.
China claims a U-shaped swathe of the sea – creating multiple overlaps with areas claimed by the Philippines, Vietnam, Brunei, Malaysia and Taiwan.
Saturday’s incident, which took place at Second Thomas Shoal (known as Ayungin in Manila and Ren’ai Reef in Beijing), is a rare glimpse into the tensions that routinely play out in the disputed waters.
Journalists on board of the Philippine ship have witnessed Chinese coast guard vessels trying to block access to a disputed shoal in the South China Sea
Journalists say they saw two Chinese coast guard ships attempt to block the path of the Philippine boat, sending a radio message, in English, warning that it was entering Chinese territory: “We order you to stop immediately, stop all illegal activities and leave.”
But instead of leaving, the Philippine boat managed to manoeuvre away and enter waters that were too shallow for the Chinese ships to follow.
The captain of the Philippine vessel, Ferdinand Gato, later told Reuters news agency that if they had not changed direction, they would have collided with one of the Chinese vessels.
Philippine troops are stationed on a beached, rusting military ship on the shoal that analysts say has become a symbol of the country marking its territory.
Two weeks ago, Manila made a formal complaint to Beijing after a similar incident when Chinese vessels succeeded in blocking a resupply mission to the shoal.
Philippine planes resorted to air-dropping food and water supplies for the soldiers stationed on board the marooned ship.
The latest confrontation was witnessed by more than a dozen journalists.
They had been invited by the Philippine military to board the government vessel to show alleged bullying by Chinese vessels in the area.
The Chinese foreign ministry condemned the Philippines for trying to “hype up” the issue, according to a statement quoted by Xinhua news agency.
The ministry accused Manila of trying to “illegally seize” the shoal.
The incident comes a day before the Philippines is due to file a case against China with the UN tribunal in The Hague, challenging its territorial claim to most of the South China Sea.
The US civilian aircrafts are expected to observe China’s rules in its newly-declared air defense zone in the East China Sea.
A statement said this did not mean the US accepted China’s requirements in the zone covering territory claimed by China, Japan, Taiwan and South Korea.
China wants all aircraft there to file flight plans and identify themselves.
The US, Japan and South Korea say they have flown military aircraft in the area unannounced. But China said it scrambled fighter jets on Friday.
The move was to monitor US and Japanese aircraft in the zone.
The US civilian aircrafts are expected to observe China’s rules in its newly-declared air defense zone in the East China Sea
The air defense identification zone (ADIZ) covers a vast area of the East China Sea, including a group of islands claimed by Japan, China and Taiwan.
South Korea claims a submerged rock, known as Ieodo, also within the zone.
The establishment of the ADIZ has caused widespread anger, with the US state department calling it “an attempt to unilaterally change the status quo in the East China Sea” which will “raise regional tensions and increase the risk of miscalculation, confrontation and accidents”.
However, on Friday, the state department said the US government “generally expects that US carriers operating internationally will operate consistent with Notams [Notices to Airmen] issued by foreign countries”.
It added: “Our expectation of operations by US carriers consistent with NOTAMs does not indicate US government acceptance of China’s requirements for operating in the newly declared ADIZ.”
Japan has instructed its aircraft not to observe China’s rules. But a number of regional commercial airlines – including Singapore Airlines, Qantas and Korean Air – have said they will comply.
China announced on Thursday it was deploying warplanes in the area for surveillance and defense.
China has scrambled fighter jets over the disputed islands in East China Sea to monitor US and Japanese planes as they flew in its newly declared air defense zone.
The zone covers territory claimed by China, Japan, Taiwan and South Korea.
China said last week that all aircraft crossing through the zone must file flight plans and identify themselves or face “defensive emergency measures”.
The US, Japan and South Korea say they have since defied the ruling and flown military aircraft in the area.
China’s newly declared air defense identification zone (ADIZ) covers a vast area of the East China Sea and includes a group of islands which are claimed by Japan, China and Taiwan.
South Korea claims ownership of a submerged rock, known as Ieodo, within the zone.
China has scrambled fighter jets over the disputed islands in East China Sea
The establishment of the ADIZ has caused widespread anger, with the US calling it a “destabilizing attempt to alter the status quo in the region”.
On Thursday, China had announced it was deploying warplanes in the area as a “defensive measure” and to carry out routine surveillance.
Then on Friday, Air Force spokesman Colonel Shen Jinke said Chinese warplanes had been scrambled that morning to identify two US surveillance aircraft and 10 Japanese planes – including early warning aircraft, surveillance aircraft and fighter jets – crossing through the ADIZ, state media reports.
Col. Shen Jinke made no reference to whether any further action was taken by any of the aircraft.
Earlier, Foreign Ministry spokesman Qin Gang said China had a right to patrol the region and that it the ADIZ was not aimed at any specific country.
Two US B-52 bombers flew over disputed islands in the East China Sea in defiance of new China’s air defense rules, officials say.
China set up its “air defense identification zone” on Saturday insisting that aircraft obey its rules or face “emergency defensive measures”.
A Pentagon spokesman said the planes had followed “normal procedures”.
The islands, known as Senkaku in Japan and Diaoyu in China, are a source of rising tension between the two nations.
Japan has dismissed the Chinese defense zone as “not valid at all” and two of its biggest airlines announced on Tuesday they would heed a request from the government in Tokyo not to implement the new rules.
US Colonel Steve Warren at the Pentagon said Washington had “conducted operations in the area of the Senkakus”.
“We have continued to follow our normal procedures, which include not filing flight plans, not radioing ahead and not registering our frequencies,” he said.
Two US B-52 bombers flew over disputed islands in the East China Sea in defiance of new China’s air defense rules
There had been no response from China, he added.
The aircraft, which were unarmed, had taken off from Guam on Monday and the flight was part of a regular exercise in the area, US defense officials said. Both planes later returned to Guam.
The US – which has more than 70,000 troops in Japan and South Korea – had previously said it would not abide by the Chinese-imposed zone.
US Defense Secretary Chuck Hagel called it a “destabilizing attempt to alter the status quo in the region”. The White House said it was “unnecessarily inflammatory”.
Japan has already lodged a strong protest over what it said was an “escalation” by China.
Taiwan, which also claims the islands, expressed regret at the Chinese move and promised that its military would take measures to protect national security.
In its statement announcing the air defense zone on Saturday, the Chinese defense ministry said aircraft must report a flight plan, “maintain two-way radio communications”, and “respond in a timely and accurate manner” to identification inquiries.
“China’s armed forces will adopt defensive emergency measures to respond to aircraft that do not co-operate in the identification or refuse to follow the instructions,” the statement said.
Japan Airlines and All Nippon Airlines said on Tuesday they would stop filing flight plans demanded by China on routes through the zone following a request from the Japanese government.
Singapore Airlines and Australia’s Qantas have both said they will abide by the new rules.
However, Australia summoned the Chinese ambassador on Tuesday to express opposition over the zone.
Australia’s Foreign Minister Julie Bishop said “the timing and manner” of China’s announcement were “unhelpful in light of current regional tensions”.
Japan’s PM Shinzo Abe has warned China that his country will respond with force if any attempt is made to land on disputed island.
The Japanese prime minister’s comments came as eight Chinese government ships sailed near East China Sea islands that both nations claim.
A flotilla of 10 fishing boats carrying Japanese activists was also reported to be in the area, as well as the Japanese coastguard.
Shinzo Abe was speaking in parliament hours after dozens of lawmakers visited a controversial war-linked shrine.
A total of 168 lawmakers paid their respects at the Yasukuni Shrine, which commemorates Japan’s war dead, including war criminals, in a move likely to anger regional neighbors who say the shrine is a reminder of Japan’s military past.
The warning from the Japanese prime minister was the most explicit to China since Shinzo Abe took power in December.
Asked in parliament what he would do if Chinese ships tried to land on the disputed islands, Shinzo Abe said they would be expelled by force.
Japan’s PM Shinzo Abe has warned China that his country will respond with force if any attempt is made to land on disputed island
“Since it has become the Abe government, we have made sure that if there is an instance where there is an intrusion into our territory or it seems that there could be landing on the islands then we will deal will it strongly,” he said.
The warning came as eight Chinese ships sailed around the islands – called Senkaku in Japan and Diaoyu in China.
The Japanese coast guard said it was the highest number of Chinese boats in the area since Tokyo nationalized part of the island chain in September 2012.
China said its ships had been monitoring Japanese vessels. The State Oceanic Administration issued a statement saying three of its ships had “found” several Japanese ships around the islands and “immediately ordered another five ships in the East China Sea to meet the three ships”.
Ten Japanese boats carrying around 80 activists arrived in the area early on Tuesday, Reuters news agency reported, monitored by Japanese Coast Guard vessels. Public broadcaster NHK said the boats were carrying “regional lawmakers and members of the foreign media”.
Japan’s top government spokesman said the “intrusion into territorial waters” was “extremely regrettable”. Japan also summoned the Chinese ambassador to protest, reports said.
The territorial row has been rumbling for years but was reignited last year when Japan bought three of the islands from their private Japanese owner.
China claims the island chain, which is controlled by Japan. Taiwan also claims the islands, which offer rich fishing grounds and lie in a strategically important area.
The dispute has led to serious diplomatic tension between China and Japan, most recently in January when Japan said a Chinese frigate locked weapons-controlling radar on one of its navy ships near the islands – something China disputes.
The visit to the Yasukuni Shrine on Tuesday by lawmakers marking the spring festival is also likely to hit ties between Beijing and Tokyo.
Two cabinet ministers, including Deputy Prime Minister Taro Aso, visited the shrine on Sunday. PM Shinzo Abe did not visit but made a ritual offering.
South Korea subsequently cancelled a proposed visit by its foreign minister, while China lodged “solemn representations” in response to the ministers’ visit.
“Only when Japan faces up to its aggressive past can it embrace the future and develop friendly relations with its Asian neighbors,” Foreign Ministry spokeswoman Hua Chunying said on Monday.
But Japanese lawmaker Hidehisa Otsujji said it was “natural” for “lawmakers to worship at a shrine for people who died for the nation”.
“Every nation does this. I don’t understand why we get a backlash,” he said.
China starts running tourism cruises to Paracel Islands, a chain of disputed islands in the South China Sea by next month, state media reports.
Chinese news agency Xinhua said tourists would live on board ships, as the largest island has only one hotel and no fresh water.
The islands, known in China as Xisha but the Paracels elsewhere, are claimed by China, Vietnam and Taiwan.
China has controlled Paracel Islands since a short war with South Vietnam in 1974.
In recent years tensions have been rising over the over-lapping territorial claims in the South China Sea, amid a more assertive stance from China.
The islands, known in China as Xisha but the Paracels elsewhere, are claimed by China, Vietnam and Taiwan
Analysts view the latest move as another step in China’s battle to demonstrate that the potentially oil-rich area is Chinese.
Xinhua quoted the Haihang Group ship company as saying that a 47,000-tonne ship, capable of accommodating nearly 2,000 passengers, was ready to sail and that another was being built.
The first tours would take place ahead of the May Day holiday, said Tan Li, the executive vice governor of Hainan province, just north of the islands.
Tan Li said tourists would eat and sleep on the ship but visit land for sightseeing, Xinhua reports, and that the currently limited facilities would be improved by the addition of more ports and sanitation infrastructure.
China claims a U-shaped swathe of the sea that extends well into what UNCLOS (UN Convention on the Law of the Sea) recognizes as the 200-mile-from-shore Exclusive Economic Zones of other claimants.
Last year, Beijing set up a local government office on the largest island, Yongxing – known in English as Woody Island – to oversee its territorial claims, a move which angered Vietnam.
And in March this year, Vietnam said China had fired on one of its fishing boats in the area, setting it alight.
China said the Vietnamese boats were illegally fishing in what it says is its territory when the incident occurred on March 20, and that it had fired flares not weapons.
Last year, the Philippines and China engaged in a lengthy stand-off over another disputed area, the Scarborough shoal, in a spat that left diplomatic ties very strained.
The South China Sea, seen to be rich in oil and natural gas reserves, has been a source of maritime conflict between several countries.
Dozens of Taiwanese boats sailed to disputed East China Sea islands in a brief protest, as top Japanese and Chinese diplomats met in Beijing to ease tensions.
The islands, called Senkaku in Japan and Diaoyu in China, are controlled by Japan but claimed by China and Taiwan.
Tension in the region has been high since Japan’s purchase of the islands from their private Japanese owner.
Taiwanese vessels, including coastguard ships, have now left the area.
Meanwhile Japanese Vice-Foreign Minister Chikao Kawai, who is in Beijing for a two-day visit, is meeting Chinese counterpart Zhang Zhijun, amid a row that has seen anti-Japanese protests in several Chinese cities.
Dozens of Taiwanese boats sailed to disputed East China Sea islands in a brief protest
Chinese surveillance and fishing boats have also been sailing in and out of waters around the islands in recent days, following the Japanese government’s announcement that it had bought the islands.
The row over ownership of the islands has been rumbling for years and has flared sporadically.
A spokesman from Taiwan’s Coast Guard Administration said that 58 fishing vessels arrived in the disputed waters at around 05:00 a.m. local time after setting off from a northern Taiwanese port on Monday afternoon.
The fishing boats were accompanied by several Taiwanese coast guard vessels.
Japan’s coast guard said warnings were issued to the boats and television footage showed water being sprayed towards the Taiwanese ships.
The flotilla turned back towards Taiwan after being in the area for a few hours, reports said.
The move to sail to the disputed area, activists and fishermen said, was to protect fishing rights and access to traditional fishing grounds.
“Fishing rights are more important than sovereignty, but fishing rights also means sovereignty [in this case],” activist Chen Chunsheng, who is organizing the flotilla, told reporters on Monday.
”So for this day on which we negotiate fishing rights, we are willing to be the backing of the government.”
Both China and Taiwan say they have inherited historic sovereignty over the islands.
The Japanese government moved to buy the islands in response to a potentially much more provocative plan by right-wing Tokyo Governor Shintaro Ishihara to buy and develop them using public donations.
The row comes at a time when both China and Japan are facing political changes domestically, making it difficult for either side to be seen as backing down.
Japanese Prime Minister Yoshihiko Noda’s government – already hit by poor figures in opinion polls – is likely to face an election in coming months. China is due to hold a party congress in weeks that will see major changes in the top echelons of leadership.
Arriving in Beijing on Monday, Japan’s envoy Chikao Kawai stressed the importance of bilateral ties.
“Because of the current difficult situation, I plan to explain what Japan is now considering to Zhang Zhijun and listen to what China is considering, for the importance of the relationship between both countries,” he said.
Chinese Foreign Ministry spokesman Hong Lei said Beijing would set out its position: “China will urge Japan to correct their mistakes and make efforts in improving ties,” he said.
A ceremony to mark 40 years of ties with Japan – due on Thursday – has been put off.
Last week, several major Japanese companies briefly suspended operations in China after attacks on shops and car dealerships.
This led to fears over a larger impact on trade between China and Japan, which is worth about $345 billion.
Most Japanese companies have resumed their operations in China. But China’s customs officials are to step up inspection of Japanese air cargo arriving at Beijing airport, said a Kyodo news report citing unnamed Japanese businesses sources.
Japan will seek compensation from China for damages to its diplomatic missions there during protests over disputed islands, Chief Cabinet Secretary Osamu Fujimura has said.
Osamu Fujimura told reporters in Tokyo that “this was an issue between the governments”.
It comes as China expressed regret over protesters attacking the US ambassador’s car in Beijing on Tuesday.
Chinese dissident and artist Ai Weiwei filmed the attack, a copy of which was uploaded on YouTube.
Japan will seek compensation from China for damages to its diplomatic missions there during protests over disputed islands
Tensions have been high between Japan and China after Japan purchased three of the disputed islands, known as Senkaku in Japan and Diaoyu in China, from a private owner.
Both Japan and China, as well as Taiwan, claim the uninhabited but resource-rich islands that are controlled by Japan.
Over the last week anti-Japanese protests in China have forced Japanese businesses to close or scale down operations.
In some cities on Tuesday, Japanese shops were attacked and vandalized on the anniversary of an incident in 1931 which led to Japan’s invasion of north-east China. The protests appeared to have diminished on Wednesday.
“Regarding damage to our embassies and consulates, we plan to demand compensation [from China] as it is an issue between the governments,” Osamu Fujimura is quoted as saying in Tokyo.
He added that any damage to Japanese property in China should be handled under local laws.
Osamu Fujimura also said that the Japanese prime minister is planning to send a special envoy to China as part of efforts “to resolve the issue cool-headedly through various diplomatic routes”.
When asked whether China would pay for damages related to the protests, Chinese Foreign Ministry spokesman Hong Lei said that relevant cases would be handled appropriately, state-run news agency Xinhua reports.
Meanwhile, China has expressed regret over the incident involving protesters that attacked US Ambassador Gary Locke’s car in Beijing on Tuesday, the US State Department said.
Its spokeswoman, Victoria Nuland, said that the US had registered its concern with China over the incident in Washington and Beijing.
Protesters chanted anti-American slogans and said that the disputed islands were part of Chinese territory as they tried to prevent the car from entering the embassy.
Ai Weiwei said he was able to shoot video footage of the attack from a friend’s place nearby.
Hong Lei said that the incident was an “individual case”, and that they were investigating it.
The US, which is an ally of Japan, has said that it would remain neutral on the islands dispute.
Two Chinese patrol ships have been sent to islands disputed with Japan, which has sealed a deal to purchase the islands, China’ state media says.
The ships had reached waters near the islands – known as Senkaku in Japan and Diaoyu in China – to “assert the country’s sovereignty”, Xinhua news agency said.
Japan confirmed on Tuesday it had signed a contract to buy three of the islands from their private owner.
Tension has been rumbling between the two countries over the East China Sea.
Japan controls the uninhabited but resource-rich islands, which are also claimed by Taiwan. Some had been in the hands of a private Japanese owner but the government says it has now signed a purchase contract.
Two Chinese patrol ships have been sent to islands disputed with Japan, which has sealed a deal to purchase the islands
“This should cause no problem for Japan’s ties with other countries and regions,” said Chief Cabinet Secretary Osamu Fujimura.
“We have absolutely no desire for any repercussions as far as Japan-China relations are concerned. It is important that we avoid misunderstanding and unforeseen problems.”
Osamu Fujimura told reporters that the government had set aside 2.05 billion yen ($26 million) to pay for the three islands.
Japan said on Monday that it was buying the islands to promote their stable and peaceful management – a move that followed a bid by the outspoken and right-wing Tokyo Governor Shintaro Ishihara to buy them using public donations.
China has called Japan’s move illegal and warned it would affect ties.
State-run media has carried strongly worded statements on the issue.
“The Chinese government will not sit idly by watching its territorial sovereignty being infringed upon,” the Foreign Ministry said in a statement issued on Monday and carried by Xinhua.
“Should the Japanese side insist on going its own way, it shall have to bear all serious consequences arising therefrom.”
Chinese Premier Wen Jiabao also reiterated China’s stand on Monday.
“The Diaoyu islands are an inalienable part of China’s territory, and the Chinese government and its people will absolutely make no concession on issues concerning its sovereignty and territorial integrity,” he said.
The announcement of the dispatch of the patrol boats came in a brief Xinhua report.
China Marine Surveillance – a maritime law enforcement agency – had “drafted an action plan for safeguarding the sovereignty and would take actions pending the development of the situation”, it said.
A small group of protesters were said to have gathered at the Japanese embassy in Beijing to protest against the purchase.
The islands, which lie south of Okinawa and north of Taiwan, sit in key shipping lanes and are thought to lie close to gas deposits.
Japan’s government has reached a deal to buy disputed islands in the East China Sea from their private owner, local media reports.
The government will pay 2.05 billion yen ($26 million) to buy islands known as Senkaku in Japan and Diaoyu in China.
There was no confirmation from officials, but the reports were carried by major Japanese media outlets, citing government sources.
The outspoken Tokyo governor had also been seeking to buy the islands.
The Japanese government will pay 2.05 bn yen ($26 million) to buy islands known as Senkaku in Japan and Diaoyu in China
Shintaro Ishihara had been collecting public donations for the purchase by the Tokyo metropolitan government, amid high tensions with China over the island chain.
At a regular press conference, Chief Cabinet Secretary Osamu Fujimura said the government and owner were in talks but would not comment on details of the discussion.
“We are negotiating with the owner while we try to grasp where the situation stands between [the central government] and the Tokyo metropolitan government,” he said.
An announcement would be made “when we reach a result after completing the process”, he said.
Kyodo news agency, citing government sources, said the agreement to buy three of the five main islands was reached with the owner on Monday.
A formal purchase contract would likely be exchanged by the end of this month, it said.
The cabinet will approve the deal in the middle of this month, both the Asahi and Yomiuri newspapers said.
The Japanese government says it has no plans to build on the islands, unlike Shintaro Ishihara who had suggested he could build a dock.
The purchase is likely to raise tensions with China, but less so than were Shintaro Ishihara to buy them.
Japan controls the islands, which lie south of Okinawa and north of Taiwan, but China also claims them, as does Taiwan.
Earlier this month, a group of Hong Kong activists landed on one of the islands amid the rumbling row. Japanese nationalists also subsequently visited, sparking protests in several Chinese cities.
On Tuesday, two men were held in Beijing for ripping the flag off the Japanese ambassador’s car, in an apparent protest over the islands.
The disputed islands sit in key shipping lanes and are thought to lie close to gas deposits.
On Wednesday an editorial in China’s Communist Party mouthpiece the People’s Daily accused Japan of acting in a two-faced manner over the islands.
“It will be difficult to improve the strained China-Japan relations if the Japanese government continues to adopt the two-faced approach of expressing goodwill on the one hand and allowing right-wing forces to kidnap the government and public opinion on the other hand,” it said.
Japanese politicians have set sail for a group of disputed islands, in the teeth of protests by China which claims them for its own.
A flotilla of some 20 Japanese boats set out for the Senkaku (Chinese: Diaoyu) islands and is expected to anchor off them early on Sunday.
The politicians plan to commemorate Japanese dead in World War II, when Japan occupied eastern China.
But Japan’s government has denied them permission to land on the islands.
China says the event will undermine its “territorial sovereignty” and this is the latest move in an escalating dispute over the islands.
On Friday, Japan deported several Chinese activists who had landed there this week.
Japanese politicians have set sail for a group of disputed islands, in the teeth of protests by China which claims them for its own
The islands, also claimed by Taiwan, are close to strategically important shipping lanes, offer rich fishing grounds and are thought to contain oil deposits.
Emotions have been running high since the commemoration on Wednesday of Japan’s surrender in World War II, when China and South Korea both protested against a visit to a Tokyo war shrine by two Japanese cabinet members.
Just before 21:00, the 150-strong party sailed out of the Japanese port of Ishigaki.
They are expected to arrive off the disputed islands in the East China Sea at dawn on Sunday.
“I want to show the international community that these islands are ours,” Kenichi Kojima, a local politician from Kanagawa, near Tokyo, told AFP news agency before he boarded.
“It is Japan’s future at stake.”
Chinese foreign ministry spokesman Qin Gan said: “Any unilateral action taken by Japan on the Diaoyu Islands is illegal and invalid.”
Earlier this week, activists sailed to the disputed island chain from Hong Kong in a protest aimed at promoting Chinese sovereignty.
China had praised Japan’s “wise” decision to free them, saying in an article on Xinhua news agency’s website that the speedy action had averted a deterioration in relations.
Rows over the disputed islands have caused Sino-Japanese ties to freeze in the past.
China claims the largely uninhabited islands has been a part of its territory since ancient times but Japan says it took control of the archipelago in the late 1890s after making sure they were uninhabited.
In September 2010, relations plummeted after the arrest of a Chinese trawler captain near the islands.
The captain was accused of ramming two Japanese patrol vessels in the area, but Japan eventually dropped the charges against him.