North Korea is suspected to have carried out yet another nuclear detonation as a quake of magnitude 6.3 was detected from the test site region. The alleged artificial quake was identified at 12.30am local time in the areas around the North Hamgyeong province, according to South Korea's weather agency.
While it was initially reported that the tremor was of magnitude 5.6, the USGS has then revised it to 6.3. This was also echoed by China's Earthquake Administration. Seoul's presidential office doubts this could be the North's sixth nuclear test. The South Korean military has been placed on high alert.
South Korean President Moon Jae-in has convened a session of the National Security Council (NSC) over the situation.
A second quake of magnitude 4.6 was also detected shortly after the first seismic wave. Japan's foreign minister has confirmed the tremor was triggered by North Korea's nuclear test.
Japan has deployed forces to check for radiation levels in the region. Prime Minister Shinzo Abe was quick to express condemnation. The Japanese leader said it was unacceptable for the North to press ahead with its programme.
The North had conducted so far five nuclear detonations in the past and two of them were carried out in 2016. Earlier reports said there were indications suggesting the North had been preparing for its sixth nuclear test.
The latest nuclear detonation takes place hours after the country claimed to have fully developed a nuclear-tipped intercontinental ballistic missile (ICBM). Pyongyang's state media outlet published a photograph of Kim Jong-un inspecting a miniaturised version of an H-bomb.