Foreign minister Wang Yi has also said if war occurs, there can be no winner.
Mr Wang’s comments come as the US voices increasing concern at North Korea’s development of nuclear weapons. A US Navy carrier group has also been deployed off the Korean peninsula.
China fears conflict could cause the regime to collapse and create problems on its border.
Mr Wang said: “One has the feeling that a conflict could break out at any moment.
“I think that all relevant parties should be highly vigilant with regards to this situation.”
“We call on all parties to refrain from provoking and threatening each other, whether in words or actions, and not let the situation get to an irreversible and unmanageable stage.”
The comments from China’s foreign minister also came after North Korea’s vice-foreign minister said President Donald Trump’s tweets were adding fuel to a “vicious cycle” of tensions on the Korean peninsula, North Korea’s vice-foreign minister has said.
And Hang Song Ryol warned that if the US showed any sign of “reckless” military aggression, Pyongyang would be ready to launch a pre-emptive strike of its own.
The vice-minister said Pyongyang had determined that the Trump administration was “more vicious and more aggressive” than that of his predecessor, Barack Obama. He added that North Korea would keep building up its nuclear arsenal in “quality and quantity” and said Pyongyang was ready to go to war if that is what Trump wants.
Tensions between Pyongyang and Washington go back to President Harry Truman and the 1950-53 Korean War, which ended in an armistice, not a peace treaty. But the heat has been rising rapidly since Trump took office in January.
This year’s joint war games between the US and South Korean militaries are the biggest ever, the USS Carl Vinson aircraft carrier has been diverted back to the waters off Korea after heading for Australia, and US satellite imagery suggests the North could conduct another underground nuclear test at any time.
Pyongyang recently launched a long-range ballistic missile and claims it is close to perfecting an intercontinental ballistic missile and nuclear warhead that could attack the US mainland.
Many experts believe that at its current pace of testing, North Korea could reach that potentially game-changing milestone within a few years – under Trump’s watch as president.
Despite reports that Washington is considering military action if the North goes ahead with another nuclear test, the vice-foreign minister did not rule out the possibility of a test in the near future.
“That is something that our headquarters decides,” he said in Pyongyang, which is now gearing up for a major holiday – and possibly a big military parade – toay. “At a time and at a place where the headquarters deems necessary, it will take place.”
The North conducted two such tests last year alone. The first was of what it claims to have been a hydrogen bomb and the second was its most powerful ever.
The annual US-South Korea military exercises have consistently infuriated the North, which views them as rehearsals for an invasion.
Washington and Seoul deny that, but reports that exercises have included “decapitation strikes” aimed at the North’s leadership have fanned Pyongyang’s anger. Officials said Trump’s tweets had also added fuel to the flames. Trump posted a tweet on Tuesday in which he said the North was “looking for trouble”.