Japan has accused China of violating its airspace for the first time after a Chinese government plane flew near disputed East China Sea islands.
Fighter jets were scrambled after the plane was seen around 11:00 local time near one of the islands, spokesman Osamu Fujimura said.
Japan lodged an immediate protest with Beijing, he said.
The islands, known as Senkaku in Japan and Diaoyu in China, have been a long-standing source of tension.
A total of eight F-15 fighters were sent after reports of the presence of the plane, which belong to China’s State Oceanic Administration – a state body tasked with law enforcement in Chinese waters.
Japan’s defence ministry said it was the first intrusion into Japan’s air space by a Chinese government aircraft since the military began keeping records, public broadcaster NHK reported.
Last year, Japan said two Chinese military planes flew near the area, but did not enter the country’s airspace.
Osamu Fujimura called the incident “extremely deplorable”, saying it followed a report from the coast guard that Chinese surveillance ships had also been seen in waters near the islands earlier in the day.
“It is extremely regrettable that, on top of that, an intrusion into our airspace has been committed in this way,” he said.
The Chinese ambassador in Tokyo had been summoned to hear a formal Japanese protest, he said.
China’s Foreign Ministry spokesman Hong Lei, however, said during a regular news briefing that the plane’s flight was “completely normal”.
“The Diaoyu islands and affiliated islands are part of China’s inherent territory,” he said.
“The Chinese side calls on Japan to halt all entries into water and airspace around the islands.”
Japan controls the islands, which are also claimed by Taiwan. Close to strategically important shipping lanes, the waters around the islands also offer rich fishing grounds and are thought to contain oil deposits.
The dispute over their ownership has rumbled for years but the Japanese government’s acquisition of three of the islands from their private Japanese owner in September sparked a renewed row, triggering a diplomatic chill and public protests in some Chinese cities.
Since then Chinese ships have been sailing in and out of waters around the islands, prompting warnings from Japan.
It is not clear whether this is a move by the Chinese side to escalate the dispute, or a one-off event designed to remind Japan of unsettled history.
Today marks the 75th anniversary of the start of the Nanjing massacre, where Japanese troops killed tens of thousands of Chinese civilians in China’s old capital, Nanjing, in 1937.
The incident also comes days before a Japanese general election thought likely to result in a change of government in Tokyo.
US defence secretary Leon Panetta has warned territorial disputes in East Asia have the potential to become wider conflicts if provocations are not reduced.
“A misjudgement on one side or the other could result in violence, and could result in conflict,” Leon Panetta said at the start of an Asian tour.
His comments came as anti-Japanese protests continue to sweep China over a disputed island chain.
Demonstrators gathered in cities across China for a second day on Sunday.
Riot police used tear gas and water cannon in the southern city of Shenzhen to break up an angry crowd.
China is reasserting its claim to sovereignty over the disputed Senkaku or Diaoyu islands in the East China Sea, in the wake of a Japanese government decision last week to purchase the islands from their private Japanese owners.
US defence secretary Leon Panetta has warned territorial disputes in East Asia have the potential to become wider conflicts if provocations are not reduced
Japanese Prime Minister Yoshihiko Noda has urged Beijing to take steps to protect Japanese nationals, but added that the authorities in both countries should “remain calm”.
Speaking in Tokyo, Leon Panetta said: “I am concerned that when these countries engage in provocations of one kind or another over these various islands, that it raises the possibility that a misjudgement on one side or the other could result in violence, and could result in conflict.”
“And that conflict would then have the potential of expanding,” he warned.
The US defence chief stressed that during his talks in Tokyo and later in Beijing he would appeal for restraint.
Leon Panetta also said that Washington did not take a position with regard to the territorial disputes in Asia.
He will also visit New Zealand as part of his tour.
On Sunday, hundreds of Chinese protesters again faced off against riot police at the Japanese embassy in Beijing.
In Shenzhen, police fired tear gas to disperse a demonstration, while in the nearby city of Guanghzhou angry crowds burned Japanese flags.
One eyewitness in the city of Xi’an described how his camera was snatched from him and damaged because it was a Japanese brand.
“Japanese-made cars were randomly stopped, their drivers grabbed and thrown out… and the cars smashed and burned. The police and army seemed to do little to stop the riot,” he said.
Tensions have been heightened this week after the purchase of some of the islands by the Japanese government from their private Japanese owners.
China briefly sent six surveillance ships into waters around the islands on Friday in response.
The islands are also claimed by Taiwan and have been a long-running source of friction in the region.
Analysts see Japan’s decision to buy the islands as damage limitation in response to a much more provocative plan by the nationalistic governor of Tokyo, who wanted to purchase and develop the islands.
And yet there is virtually no mention of the protests in China’s state media, and attempts have been made to control discussion on the internet.
This reflects the Communist leadership’s ambivalence about such displays of nationalist fury: they can be useful to send a message to Japan, but could easily get out of control and spark wider expressions of discontent.
There is plenty of scope for miscalculation in the coming days: Chinese fishing fleets are set to return to the disputed waters, and nationalists could try to provoke Japan by landing on the islands.
In Japan, the government seems unlikely to back down with election looming.
There is talk in the Japanese press that some on both sides could be willing to risk a limited naval clash in defence of the conflicting claims.
Further complicating matters, Japan’s newly appointed ambassador to China, 60-year-old Shinichi Nishimiya, died on Sunday, the foreign ministry said.
The envoy – who had been due to take his post in October – collapsed several days earlier near his Tokyo home and was taken to hospital.
The foreign ministry has not publicly commented on what caused his death.
Six Chinese surveillance ships have entered waters near islands claimed by both Japan and China.
China said the ships were carrying out “law enforcement” to demonstrate its jurisdiction over the islands, known as Diaoyu in China and Senkaku in Japan.
At least two of the vessels left after the Japanese coast guard issued a warning, Japanese officials say.
The move came after Japan sealed a deal to buy three of the islands from their private Japanese owner.
Japan controls the uninhabited but resource-rich East China Sea islands, which are also claimed by Taiwan.
Six Chinese surveillance ships have entered waters near islands claimed by both Japan and China
The Japanese Coast Guard said the first two Chinese boats entered Japan’s territorial waters at 06:18 local time, followed by another fleet of four other ships just after 07:00.
The first two ships then left the area. A third ship left later on Friday morning, one report said. No force was used, Japanese officials added.
“Our patrol vessels are currently telling them to leave our country’s territorial waters,” the coastguard said in a statement.
The Chinese foreign ministry confirmed that its ships were there.
“These law enforcement and patrol activities are aimed to demonstrate China’s jurisdiction over the Diaoyu Islands and its affiliated islets and ensure the country’s maritime interests,” a statement said.
The US has called for ”cooler heads to prevail” as tension intensifies between China and Japan over the islands, which lie south of Okinawa and north of Taiwan.
US Defense Secretary Leon Panetta is due to visit both Japan and China from this weekend as part of a tour of the region that also includes New Zealand.
The dispute has seriously marred diplomatic relations between China and Japan and threatens to damage the strong trading relationship.
The row has also generated strong nationalist sentiment on both sides that observers say now makes it very difficult to be seen to be backing down.
The Japanese government says it is buying the islands to promote their stable and peaceful management.
Its move followed a bid by right-wing Tokyo Governor Shintaro Ishihara to buy the islands using public donations – an action that would likely have further provoked China.
China, on the other hand, says the islands have historically been its territory and fishing grounds.
Meanwhile Japan’s newly-appointed ambassador to China, Shinichi Nishimiya, remains in hospital in Tokyo after he was found unconscious near his home in Tokyo on Thursday.
No details have been given on his condition. He was appointed on Tuesday to replace Uichiro Niwa, who has been criticized for his handling of one of the worse diplomatic rows between Japan and China in recent years.
Japan-China disputed islands:
• The archipelago consists of five islands and three reefs
• Japan, China and Taiwan claim them; they are controlled by Japan and form part of Okinawa prefecture
• The Japanese government signed a deal in September 2012 to purchase three islands from Japanese businessman Kunioki Kurihara, who used to rent them out to the Japanese state
• The islands were the focus of a major diplomatic row between Japan and China in 2010
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.