The earthquake, which appeared to have occurred naturally, was detected 41 kilometres (25 miles) northwest of Kilju, which is home to the nuclear test site, Yonhap said, citing the Korea Meteorological Administration.

The quake was detected at 7:00 pm (1000 GMT) at a depth of 20 kilometres (12 miles).

North Korea conducted six nuclear tests at the Punggye-ri nuclear test facility between 2006 and 2017.

The 2017 nuclear test triggered a much bigger 6.3 magnitude quake that was felt across the border in China.

The 2017 test sparked global condemnation, leading the United Nations Security Council to unanimously adopt new sanctions that included restrictions on oil shipments.

Monitoring groups estimated the sixth nuclear test had a yield of up to 250 kilotons, which is 16 times the size of the US bomb that destroyed Hiroshima in 1945.

Following the 2017 test, the North claimed it had detonated a hydrogen bomb "of unprecedently big power", saying it marked a "very significant occasion" in achieving the "final goal" of becoming a complete nuclear power.

US intelligence officials estimated in 2018 that Pyongyang had enough fissile material -- the core component of nuclear weapons -- for 65 weapons, and that it produces enough fissile material for 12 additional weapons every year.

A 2021 report from the RAND Corporation projected that North Korea could have more than 200 nuclear weapons and hundreds of ballistic missiles stockpiled by 2027.