China declared a "red line" on North Korea on Saturday, saying that China will not permit chaos or war on the Korean peninsula, and that peace can only come through denuclearisation.

China is North Korea's most important diplomatic and economic supporter, though Beijing's patience with Pyongyang has been severely tested following three nuclear tests and numerous bouts of sabre rattling, including missile launches.

"The Korean peninsula is right on China's doorstep. We have a red line, that is, we will not allow war or instability on the Korean peninsula," Chinese Foreign Minister Wang Yi told reporters on the sidelines of China's annual largely rubber-stamp parliament.