China has warned against "troublemaking" on its doorstep, in an apparent rebuke to North Korea.
The United States has said it was postponing a missile test to help calm high tension on the divided Korean peninsula.
The North, led by 30-year-old Kim Jong-un, has been issuing vitriolic threats of war against the US and US-backed South Korea.
The threats have been taking place since the United Nations imposed sanctions in response to its third nuclear weapon test in February.
Pyongyang's anger appears heightened by US-South Korean joint military exercises.
China, North Korea's sole financial and diplomatic backer, has shown growing irritation with Pyongyang's warnings of nuclear war.
Chinese President Xi Jinping, did not name North Korea but said no country "should be allowed to throw a region and even the whole world into chaos for selfish gain".
Stability in Asia, he said, "faces new challenges, as hot spot issues keep emerging and both traditional and non-traditional security threats exist".
Chinese Foreign Minister Wang Yi expressed similar frustration in a statement late yesterday, relating a telephone conversation with UN Secretary-General Ban Ki-moon.
Mr Wang said: "We oppose provocative words and actions from any party in the region and do not allow trouble making on China's doorstep."
Today, the ministry expressed "grave concern" at rising tension and said China had asked North Korea to "ensure the safety of Chinese diplomats in North Korea, in accordance with the Vienna Convention and international laws and norms".
China's embassy, it said, was "understood" to be operating normally in Pyongyang.
Most analysts say it has no intention of starting a conflict.
A conflict would bring its own destruction and instead is out to wring concessions from a nervous international community.
The North told diplomats late last week to consider leaving Pyongyang because of the tension, but embassies appeared to view the appeal as more rhetoric and staff have stayed put.
South Korea has said it was ready for any kind of action that the North's unpredictable leaders might make.
Action anticipated could include a possible missile launch by Wednesday.
After which day the North said it could not guarantee diplomats' safety.
Australian Prime Minister Julia Gillard said avoiding conflict on the peninsula was vital.
She said:"There, any aggression is a threat to the interests of every country in the region."
British Foreign Minister William Hague said North Korea's nuclear ambitions had to be taken seriously.
The US had decided to delay a long-planned missile test scheduled for next week out of California "to avoid any misperception or miscalculation" given tensions with North Korea.
A senior US defence official announced the decision yesterday.
The unusual precaution by the United States follows recent hostile statements from North Korea, including the threat of open war.
It also came after reports in South Korea that the North, under its 30-year-old leader, Kim Jong-un, had moved two medium-range missiles to a location on its east coast.
The White House said on Friday it would "not be surprised" if the North staged another missile test.
At the same time, officials have said there are no signs North Korea is gearing up for war, such as large-scale troop movements.