Nuclear weaponsNorth Korea claims to have tested miniaturized hydrogen bomb

North Korea has conducted its fourth nuclear test in ten years – the previous tests took place in 2006, 2009 and 2013 – indicating that the country is further along in developing nuclear warheads which could be miniaturized and placed on a missile capable of reaching the U.S. mainland.

Pyongyang pubic media outlets have claimed that what was tested was hydrogen bomb, but some experts who talked with the Telegraph say initial evidence suggests the test involved a uranium or plutonium device which was not as powerful as a hydrogen bomb.

North Korean television announced the country had successfully tested a “miniaturized hydrogen bomb” underground on Wednesday morning, describing it as an “act of self-defense” against the United States. North Kore’s claim about the type and size of device tested could not be verified independently.

Analysts note, though, that if North Korea’s claims are true, it would be the first time the North has successfully tested a hydrogen bomb and could also enable the isolated country to launch long-range nuclear missiles.

“If it’s true, it means they’ve made something smaller scale, capable of being put onto a missile, said John Carlson, the former head of the Australian Safeguards and Non-Proliferation Office. “I think we can assume the previous tests they’ve carried out have been devices too large to fit onto a missile.”

South Korea’s intelligence agency said the seismic wave the agency’s sensors picked up was more likely caused by an atomic bomb, Lee Cheol Woo, a South Korean politician, told the Telegraph.

Yang Uk, a senior research fellow at the Korea Defense and Security Forum, said: “Given the scale it is hard to believe this is a real hydrogen bomb. They could have tested some middle stage kind (of device) between an A-bomb and H-bomb, but unless they come up with any clear evidence, it is difficult to trust their claim.”

North Korea’s previous nuclear tests triggered condemnations and rounds of UN sanctions banning trade and financing activities which aid its weapons program.

North Korea, believed to have between six and ten crude nuclear bombs in its arsenal, is now facing deepening isolation and more sanctions imposed by the UN Security Council.