North Korea has threatened "physical countermeasures" against the South for backing UN sanctions adopted earlier this week.
The sanctions were passed by the UN Security Council -- on which South Korea is currently sitting -- to punish the North for a long-range rocket test on December 12.
On January 24, Pyongyang announced it is planning a third nuclear weapons test and further rocket launches that "will target our sworn enemy, the United States."
An editorial in a Chinese state newspaper said Beijing will reduce aid to the North if it conducts another nuclear test.
A Chinese Foreign Ministry spokesman said that all parties should remain calm and that five-party talks -- involving China, Russia, the United States, and North and South Korea -- should resume immediately.
Based on reporting by AFP and dpa