North Korea said on Wednesday it successfully tested a hydrogen bomb

North Korea said on Wednesday it successfully tested a hydrogen bomb, the fourth time it has detonated a nuclear device and a move that dramatically escalates tensions on the peninsula with neighbors South Korea and Japan.

The regime in Pyongyang detonated a hydrogen device for the first time at 10 am. local time, its official Korean Central News Agency said. The explosion was initially detected as a magnitude 5.1 earthquake by the US Geological Survey.

North Korea carried out the test “safely” and “perfectly,” according to KCNA, describing the detonation as an act of “self-defence” from its enemies. The regime “has confidently risen to the ranks of nuclear powers with hydrogen bombs by perfectly succeeding in the historic test of a hydrogen bomb,” Korean Central Television anchorwoman Ri Chun Hui said.

It’s the second test since Kim Jong Un became supreme leader four years ago and began consolidating power through a series of purges and provocations against South Korea. Kim has rebuffed US and Chinese efforts to restart disarmament talks and has expanded the country’s nuclear arsenal that he says is the best defense against a US invasion.

Confirmation of the detonation elevates the reclusive regime’s nuclear program toward the top of the global diplomatic agenda, with Kim possibly seeking to use the tensions to demand economic and political concessions from South Korea and the US. In a new year message only last week he had pledged to “actively” work to improve ties with the government in Seoul.

“A fourth nuclear test would allow for miniaturization and diversification of nuclear weapons so was an essential step for North Korea,” said Ahn Chan Il, who heads the World Institute for North Korea Studies in Seoul. “North Korea may be thinking it can open up for reforms only when it’s recognized as a nuclear power.”

The Korean won declined as much as 0.8 per cent to 1,197.85 per dollar, the weakest level since September. The Kospi index of shares dropped 0.6 per cent as makers of defence products such as Speco Co. surged. Ten-year bonds advanced, pushing their yield down one basis point to 2.05 per cent.