Obama warns Pyongyang of 'serious consequences' over nuke tests

Obama was briefed on the situation as he flew home from a visit to Asia aboard Air Force One

Obama warns Pyongyang of

US President Barack Obama on Friday consulted leaders of South Korea and Japan over North Korea's fifth nuclear test, which is believed to be most powerful ever, and warned Pyongyang of " serious consequences".

Josh Earnest, press secretary of White House, said: "The president indicated he would continue to consult our allies and partners in the days ahead to ensure provocative actions from North Korea are met with serious consequences."

Earnest, according to media reports, said President Obama was briefed on the situation as he flew home from a visit to Asia aboard Air Force One.

The US President consulted with South Korean President Park Geun-hye and Japans Prime Minister Shinzo Abe in separate phone calls from the presidential aircraft.

"The president reiterated the unbreakable US commitment to the security of our allies in Asia and around the world," Earnest added.

Earlier, National Security Council spokesman Ned Price said the US was monitoring and continuing to assess the situation in view of the seismic activity on the Korean Peninsula in the vicinity of a known nuclear site.

The U.S. Geological Survey and European agencies had measured an artificial earthquake, which was recorded at 0030 GMT, with a magnitude of 5.3. Agencies in China, reclusive North Korea's main diplomatic ally, also recorded the tremor, media reported.

The test came as North Korea celebrates the "day of the foundation of the republic," the 68th anniversary of the formation of the communist regime by Kim Il Sung, the current leader's grandfather.