North Korea claims successful hydrogen bomb test in 'self-defence against US'

North Korea has conducted its fourth nuclear test, the country’s state media has announced, in a move that could take it a step closer to developing nuclear warheads capable of striking the US mainland. Some experts, though, said initial evidence was pointing towards a test involving a uranium or plutonium device and not, as Pyongyang has claimed, a far more powerful hydrogen bomb.
 An announcement on North Korean television said the country had successfully tested a “miniaturised hydrogen bomb” underground on Wednesday morning, describing it as an “act of self-defence” against the US. North Korean claims about the size and type of bomb have not been independently verified.
 If the claims are true, it would be the first time the North has successfully tested a hydrogen bomb and could also enable the secretive state to launch long-range nuclear missiles. continue