North Korea says it has conducted a successful hydrogen bomb test

TOKYO - North Korea on Wednesday claimed it had successfully tested a hydrogen bomb, a claim that, if true, would mark a huge step forward in its nuclear capability.

'We've carried out a hydrogen bomb test,” a newsreader on the state-run Korean Central Television station announced in a special broadcast from Pyongyang.

'North Korea was forced to develop its nuclear arsenal because of the U.S.'s hostile policy against North Korea,” she said. 'However, as a peaceful nation and a nuclear powered nation, North Korea will be a responsible state and will not use its nuclear power before [an attack] and will not transfer the technology to others.”

There was some skepticism about the claim, with nuclear experts noting that the yield appeared to be similar to North Korea's three previous atomic tests, rather than the 'enormous” yield that would be expected if it had been a thermonuclear test.

Either way, Pyongyang's provocative action will present a new challenge to the outside world, which has struggled to find ways to end North Korea's nuclear defiance.

'North Korea's fourth test - in the context of repeated statements by U.S., Chinese, and South Korean leaders - throws down the gauntlet to the international community to go beyond paper resolutions and find a way to impose real costs on North Korea for pursuing this course of action,” said Scott Snyder, a Korea expert at the Council on Foreign Relations.

Kim Jong Un's regime hinted in December that it had built a hydrogen bomb to 'defend its sovereignty and the dignity of the nation.” Some analysts were doubtful, saying the young leader appeared primarily concerned with trying to bolster his legitimacy.

But on Wednesday, North Korea said in a special broadcast that it had carried out a 'successful” hydrogen bomb test. 'With this hydrogen bomb test, we have joined the major nuclear powers,” the newsreader said.

Hydrogen, or thermonuclear, bombs are exponentially more powerful and destructive than atomic devices. An atomic bomb uses fission to break up the atomic nucleus and release energy, while a hydrogen or thermonuclear bomb uses fusion to add to the nucleus. This leads to an enormous explosion resulting from an uncontrolled, self-sustaining chain reaction.