The UN Security Council has strongly condemned North Korea's nuclear test and is pledging to pursue new sanctions.
A statement issued by the council after emergency closed-door consultations today called the test "a clear violation" of council resolutions, adding "therefore a clear threat to international peace and security continues to exist".
The council said it had previously expressed determination to take "further significant measures" in the event of another North Korean test and would begin work immediately on a new sanctions resolution in light of "the gravity of this violation".
Earlier, the United Nations secretary-general condemned the announcement of the nuclear test, calling it ``profoundly destabilising for regional security''.
Ban Ki-moon demanded that Pyongyang cease any further nuclear activities and meet its obligations for “for verifiable denuclearisation”.
US defence secretary Ash Carter also spoke by phone to his South Korean counterpart Han Min-Koo, and they agreed that a North Korean nuclear test would be an “unacceptable and irresponsible provocation,” according to Mr Carter’s press secretary, Peter Cook.
Mr Cook said Mr Carter reaffirmed the United States’ treaty commitment to defend South Korea, which he said includes “all aspects of the United States’ extended deterrence” – an allusion to a long-standing US promise to defend South Korea with nuclear weapons if necessary.
The White House said the US government's early analysis of underground activity in North Korea ``is not consistent'' with that country's claim of having conducted a successful hydrogen bomb test, however.
Spokesman Josh Earnest also says nothing has happened to change the US government’s assessment of North Korea’s technical or military capabilities.
He said the US government is still doing the work that is needed to learn more about the nuclear test North Korea claims to have conducted successfully.