BEIJING, Feb 6 (Reuters) - China expressed serious concern on Wednesday after North Korea stepped up its bellicose rhetoric and threatened to go beyond a third nuclear test in response to what it sees as "hostile" sanctions imposed after a December rocket launch.
"China is extremely concerned by the way things are going. We oppose any behaviour which may exacerbate the situation and any acts which are not beneficial towards the denuclearisation of the Korean peninsula," said Foreign Ministry spokeswoman Hua Chunying.
"We call on all the relevant sides to remain calm and exercise restraint and earnestly work hard to maintain peace and stability in the Korean peninsula," she told a daily news briefing.
China is the North's sole remaining major diplomatic and economic benefactor but has been showing sings of exasperation with its isolated neighbour.
One of China's most widely read newspapers, the tabloid Global Times published by Communist Party mouthpiece the People's Daily, said China should take a tough line and inform North Korean leaders of the consequences of their actions.
"If North Korea insists on a third nuclear test despite attempts to dissuade it, it must pay a heavy price," it said in an editorial in both its Chinese and English-language issues.
The newspaper said China should cut its help if North Korea went ahead with the nuclear test. In 2009, China reportedly cut fuel supplies to North Korea after a nuclear test, although it was impossible to verify the reports.
"The assistance it will be able to receive from China should be reduced. The Chinese government should make this clear beforehand to shatter any illusions Pyongyang may have," the Global Times said.
While the stridently nationalist newspaper is not considered an official mouthpiece of the Chinese government, it is nonetheless an influential publication.
North Korea has vowed to conduct more rocket and nuclear tests in response to a U.N. censure for its launch of a long-range missile launch in December. On Tuesday, it vowed "stronger" but unspecified actions in addition to the test.
U.S.-backed South Korea and others who have been closely observing activities at the North's known nuclear test grounds believe it is technically ready for a nuclear test and is awaiting the final word from supreme leader Kim Jong-un.
The Chinese spokeswoman reiterated China's wished to see a nuclear-weapons-free Korean peninsula.
NORTH HAS STRUCK BEFORE
In 2010, North Korea was blamed for sinking a South Korean naval vessel. It also shelled a South Korean island in the same year, killing civilians.
The North, which frequently aims fiery rhetoric at South Korea and the United States, did not spell out the actions it would take in its comments on Tuesday.
It is not capable of staging a military strike on the United States, although South Korea is in range of its artillery and missiles and Japan of its missiles.
"The DPRK (Democratic Peoples Republic of Korea, or North Korea) has drawn a final conclusion that it will have to take a measure stronger than a nuclear test to cope with the hostile forces' nuclear-war moves that have become ever more undisguised," the North's KCNA state news agency said.
New U.S. Secretary of State John Kerry discussed North Korea in what he said were "remarkably similar" telephone conversations with his counterparts from Japan, South Korea and China, State Department spokeswoman Victoria Nuland said.
U.N. resolutions ban North Korea from developing missile or nuclear technology after its nuclear tests in 2006 and 2009.
North Korea says that it has the sovereign right to launch rockets for peaceful purposes, even though the multiple U.N. resolutions make this illegal under international law.
The North has in the past said its nuclear programme was for peaceful purposes but has more recently boasted of becoming a nuclear weapons state.
(Reporting by Koh Gui Qing and Ben Blanchard)