United Nations Security Council members, including New Zealand, have unanimously condemned North Korea's reported nuclear test, saying it's a "clear threat to international peace and security".
The 15-member council held an emergency meeting in New York on Thursday morning (NZ time) following North Korea's announcement that it had conducted a "successful" underground hydrogen bomb test.
In a statement, the council said the test was a clear violation of a number of UN resolutions and of the non-proliferation regime.
"Therefore a clear threat to international peace and security continues to exist," the council said.
It will now begin work on what further measures to impose against North Korea, such as additional sanctions, in response to the test.
UN Secretary-General Ban Ki-moon said the test is "deeply troubling".
"This act is profoundly destabilising for regional security and seriously undermines international non-proliferation efforts," he said.
"I condemn it unequivocally."
The New Zealand government has joined a chorus of international voices condemning North Korea's actions.
"The test would run contrary to the recent efforts at dialogue on the Korean peninsula and flies in the face of the international community's calls for North Korea to abandon its nuclear weapon programmes," duty minister Sam Lotu-Iiga said.
The White House says initial analysis of the test isn't consistent with North Korea's claim that it had conducted a hydrogen bomb test.
Further work is being undertaken to confirm the type of device tested.
North Korea has been subject to UN sanctions since its first nuclear test in 2006.