China has banned the export to North Korea of several weapon-related technologies which could be used in the development of nuclear weapons.
China’s Commerce Ministry published the list, which includes components for nuclear explosive devices and rocket systems, on Monday.
The ministry said the move would help implement UN resolutions on North Korea, and would be effective immediately.
Analysts say the ban shows China taking a firmer line against its ally.
China has banned the export to North Korea of several weapon-related technologies which could be used in the development of nuclear weapons
The list includes technology in nuclear, missile, chemical and biological fields.
It says the restrictions are developed in accordance with several UN Security Council resolutions on North Korea.
China is North Korea’s only ally and its major trading partner.
Western powers have previously criticized China for not rigorously enforcing UN sanctions imposed on North Korea because of its nuclear programme.
However, relations between Beijing and Pyongyang have been seriously strained in recent months.
In March, China supported a UN Security Council resolution tightening sanctions against North Korea, in response to Pyongyang’s third nuclear test in February.
The United Nations Security Council has unanimously approved fresh sanctions against North Korea in response to Pyongyang’s nuclear test last month.
The resolution is targeting North Korean diplomats, cash transfers and access to luxury goods.
It imposes asset freezes and travel bans on three individuals and two firms linked to North Korea’s military.
Pyongyang earlier vowed to use its right to a pre-emptive nuclear attack against its aggressors.
In a 15-0 vote, the council on Thursday backed Resolution 2094, imposing the new sanctions against the North.
Speaking after the vote, the US ambassador to the UN, Susan Rice, said the document “strongly condemns” Pyongyang’s actions.
Susan Rice said the sanctions would “further constrain” North Korea’s ability to develop its nuclear programme.
She warned that the UN would “take further significant actions” if Pyongyang were to carry out another nuclear test.
The UN Security Council has unanimously approved fresh sanctions against North Korea in response to Pyongyang’s nuclear test last month
“North Korea will achieve nothing by continuing threats and provocations,” she stressed, urging North Korea to comply with the demands of the international community.
China’s UN ambassador, Li Baodong, said that “the top priority now is to defuse the tensions” on the Korean peninsula.
Li Baodong also said that the six-party talks on the North’s controversial programme must resume.
South Korea’s envoy to the UN, Kim Sook, described the North’s nuclear tests as “grave threat to the peace” on the Korean peninsular and the wider region.
Kim Sook urged Pyongyang to respond to the concerns of the world community.
“North Korea’s future rests in its own hands,” he said.
Russian ambassador Vitaly Churkin, who is the current president of the council, described the resolution as an “appropriate measure”.
UN Secretary General Ban Ki-moon said the measure “sent an unequivocal message to (North Korea) that the international community will not tolerate its pursuit of nuclear weapons.”
Pyongyang has so far made no comments following Thursday’s vote.
But earlier it accused the US of pushing to start a war.
“As long as the United States is willing to spark nuclear war, our forces will exercise their right to a pre-emptive nuclear strike,” said North Korea’s foreign ministry, in a statement carried by the KCNA news agency, without giving further details.
Earlier this week, Pyongyang also threatened to scrap the 60-year truce which ended the 1950-53 Korean War.
North Korea has issued another warning, a day after announcing plans for a third nuclear test.
In a statement, Pyongyang pledged “physical counter-measures” against South Korea if it participated in the UN sanctions regime.
The threat came 24 hours after North Korea said it would proceed with a “high-level” nuclear test in a move aimed at “arch-enemy” the US.
The White House condemned the move, labelling it “needlessly provocative”.
North Korea has conducted two nuclear tests in the past, in 2006 and 2009. It gave no time-frame for its third test.
Its announcement followed the adoption by the UN Security Council of a resolution condemning North Korea’s recent rocket launch and extending sanctions.
North Korea says its rocket launch was for the sole purpose of putting a satellite into orbit; the US and North Korea’s neighbors say it was a test of long-range missile technology banned under UN resolutions.
The second warning in two days came in a statement from the Committee for the Peaceful Reunification of the Fatherland, carried by KCNA news agency.
North Korea pledged physical counter-measures against South Korea if it participated in the UN sanctions regime
“If the puppet group of traitors takes a direct part in the UN <<sanctions>>, the DPRK [North Korea] will take strong physical counter-measures against it,” it said, referring to the South Korean leadership.
“<<Sanctions>> mean a war and a declaration of war against us.”
The UN resolution, passed on Tuesday, expanded existing sanctions against Pyongyang that were imposed after its previous nuclear tests and rocket launches.
Washington has also expanded its own sanctions against North Korea, with targets including a Hong Kong-based trading company and two North Korean bank officials based in Beijing.
On Thursday, it spoke out against a third nuclear test.
“Further provocations would only increase Pyongyang’s isolation, and its continued focus on its nuclear and missile programme is doing nothing to help the North Korean people,” White House spokesman Jay Carney told reporters.
Beijing has called for dialogue, urging all parties to act with restraint and “look at the long-term interest”.
But an editorial in China’s state-run Global Times appeared to hint at exasperation.
“If North Korea engages in further nuclear tests, China will not hesitate to reduce its assistance,” the editorial said.
Both North Korea’s previous nuclear tests followed long-range rocket launches.