The BBC reports:
North Korea says it has successfully carried out its first underground test of a hydrogen bomb – a more powerful weapon than an atomic bomb. If true it would be its fourth nuclear test since 2006 and mark a huge advance in its nuclear capabilities.
The announcement was swiftly criticised by world leaders with South Korea calling it “a grave provocation to our national security”. But there has been no independent confirmation of the North’s claim yet.
Suspicion an underground test had been carried out was first raised after the US Geological Survey detected unusual seismic activity at 10:00 Pyongyang time (01:30 GMT) – in the north-east of the country. A 5.1 magnitude tremor was detected about 50km (30 miles) from Kilju city, near the Punggye-ri nuclear site, which monitors said was likely not natural.
Hours later, in a surprise announcement, a newsreader on North Korean state TV said: “The republic’s first hydrogen bomb test has been successfully performed at 10:00 am on January 6, 2016.” North Korean leader Kim Jong-un had said last month that Pyongyang had developed a hydrogen bomb, although many experts were skeptical.