North Korea's neighbours lined up today to condemn Pyongyang's claimed hydrogen bomb test, saying it posed a grave threat to regional security.
Several governments promised a firm response as tensions soared again in northeast Asia, many calling for further action by the United Nations against the hermit nation, which is already subject to heavy international sanctions.
"The nuclear test that was carried out by North Korea is a serious threat to the safety of our nation and we absolutely cannot tolerate this," Japanese Prime Minister Shinzo Abe said in Tokyo.
"This clearly violates UN Security Council resolutions and is a grave challenge against international efforts for non-proliferation," he said, adding his country would seek to coordinate efforts among UN members to deal with the action.
South Korean President Park Geun-Hye called the test a "grave provocation" at an emergency meeting of the Country's National Security Council (NSC) convened immediately after the news broke.
"The test is not only a grave provocation to our national security but also a threat to our future... And a strong challenge to international peace and stability," she said, calling for strong sanctions on Pyongyang.
In an earlier statement, Seoul said it would "take all necessary measures including additional sanctions by the UN Security Council... So that the North will pay the price for the nuclear test".
In Washington, the White House would not confirm the test, but vowed to "respond appropriately to any and all North Korean provocations".
There was no immediate response from China, North Korea's key diplomatic protector, but in a report from Pyongyang, the official Xinhua news service said that the "test apparently runs counter to relevant UN resolutions" and "is set to cause repercussions".
Australian foreign minister Julie Bishop said her country "condemns in the strongest possible terms" the test, which "confirms North Korea's status as a rogue state and a continuing threat to international peace and security", adding that Canberra would express its concerns to Pyongyang directly and call for stronger UN sanctions.
The test, which came just two days before leader Kim Jong-Un's birthday, was initially detected by international seismology monitors as a 5.1-magnitude tremor next to the North's main Punggye-ri nuclear test site in the northeast of the country.
Last month, North Korean leader Kim Jong-Un suggested Pyongyang had already developed a hydrogen bomb.
The claim was questioned by international experts and there was continued scepticism over today's test announcement.
