A large earth tremor has been detected in North Korea, raising speculation that the country has carried out its sixth nuclear test.
US seismologists said the 5.6 magnitude quake was recorded at a depth of 10km (six miles).
South Korea immediately convened a national security council meeting.
The tremor comes hours after North Korean leader Kim Jong-un was pictured with what state media said was a new type of hydrogen bomb.
South Korea officials said the quake took place in Kilju County, where the North’s Punggye-ri nuclear test site is situated.
China’s Earthquake Administration described the tremor as a “suspected explosion”.