China on Monday condemned what it described as North Korea's "brazen" nuclear test.
"On October 9, the DPRK (North Korea), ignoring the general opposition of the international community, brazenly undertook a nuclear test," a foreign ministry statement said.
"The Chinese government expresses its resolute opposition.
"China strongly demands the DPRK side to undertake its commitments to the non-nuclearisation of the Korean Peninsula, and stop all actions that can lead to the deterioration of the situation."
China also called on North Korea to return to the six-party talks aimed at reining in Pyongyang's nuclear program.
North Korea pulled out of the talks - involving the two Koreas, China, the United States, Japan and Russia - in November 2005.
China urged all nations to react peacefully to North Korea's nuclear test.
"The Chinese government calls on all sides to deal with this calmly and seek consultations to peacefully resolve the issue. The Chinese side will continue to make unremitting efforts towards this end," it said.