Foreign Ministry spokeswoman Hua Chunying briefs media on the DPRK nuclear test issue during a daily press briefing in Beijing, Jan 6, 2016. WANG ZHUANGFEI/CHINA DAILY

Foreign Minister Wang Yi said that "China firmly champions the international nuclear nonproliferation system".

The United Nations Security Council has planned an emergency meeting on Wednesday in New York. US National Security Council spokesman Ned Price said Washington will respond appropriately to any "provocations".

Russia's Foreign Ministry said it hadn't been confirmed that the DPRK had carried out an actual nuclear test, and that all sides should "preserve maximum restraint", AFP reported.

An official in Seoul points at where seismic waves were observed in the Republic of Korea on Wednesday. REUTERS

Republic of Korea President Park Geun-hye said on Wednesday that Seoul "should closely cooperate with the international community", ROK's Yonhap news agency reported.

Yu Meihua, director of the Center for Korean Peninsula Peace Studies of the China Reform Forum, said the United States and its allies Japan and the ROK will take Pyongyang's test as an excuse to "initiate the next arms race in the region" by having more military cooperation and deployment in the region.

Yu said fresh UN sanctions might be imposed and "DPRK's pace of economic cooperation with foreign countries will possibly see a slowdown".

Zhang Liangui, an expert of Korean studies at the Party School of the Central Committee of the Communist Party of China, said the nuclear test was "not a surprise", as Pyongyang has renewed commitment to its nuclear plans in recent years.

AFP and Xinhua contributed to this story.