UN to hold emergency talks on N Korea

The closed-door morning talks between the 15 member nations were called by the United Nations and Japan.

US mission spokesperson Hagar Chemali said: "While we cannot confirm at this time that a test was carried out, we condemn any violation of UNSC Resolutions and again call on North Korea to abide by its international obligations and commitments."

If the test was indeed a hydrogen bomb, it would be more powerful than anything the North has ever tested, marking a significant increase in capabilities.

The hermit state previously tested far less powerful fission blasts generated by uranium or plutonium.

A hydrogen, or thermonuclear device, uses fusion in a chain reaction.

If North Korea's claim is confirmed, it would massively raise the stakes around its banned nuclear programme.

Strong reaction

France slammed North Korea's testing of a nuclear bomb as an "unacceptable violation" of UN Security Council resolutions and called for a "strong reaction from the international community".

The presidency said: "While awaiting confirmation of the characteristics of the nuclear test announced and observed in North Korea, France condemns this unacceptable violation of (UN) Security Council resolutions and calls for a strong reaction from the international community".

British Foreign Secretary Philip Hammond on Wednesday described North Korea's nuclear test as a "provocation" and a "grave" breach of United Nations Security Council resolutions.

Hammond wrote on Twitter: "If North Korean H-bomb test reports are true, it is a grave breach of UNSC (UN Security Council) resolutions and a provocation which I condemn without reservation".

The British foreign secretary, who is on an official visit to key North Korean ally China, said London and Beijing would co-ordinate their reaction to the test.

"I have discussed this matter today (on Wednesday) in Beijing with my Chinese counterpart Yang Jiech and we have agreed to work with other members of the UN Security Council towards a robust international response," Hammond said in a statement.

Hammond is due to speak with his Japanese and South Korean counterparts on Wednesday and visit Tokyo for meetings later this week, the statement said.

China is a key diplomatic protector of Pyongyang, though relations have been strained in recent years, partly due to North Korea's continuance of its nuclear programme despite international opposition.

Serious threat

South Korean President Park Geun-Hye described the test as 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".

Japanese Prime Minister Shinzo Abe slammed the test as "a serious threat to the safety of our nation".

"This clearly violates UN Security Council resolutions and is a grave challenge against international efforts for non-proliferation," he said in Tokyo, adding his country would seek to coordinate efforts among UN members to deal with the action.

In Washington, the White House would not confirm the test, but vowed to "respond appropriately to any and all North Korean provocations".

Whether an H-bomb or not, it was North Korea's fourth nuclear test and marked a striking act of defiance in the face of warnings that Pyongyang would pay a steep price if it continued pursuing its atomic weapons programme.

The three previous tests in 2006, 2009 and 2013 triggered waves of UN sanctions. Their failure to prevent a fourth detonation will see calls for more drastic Security Council action this time around