Large quake reported near nuclear testing site in North Korea
International monitoring agencies have reported an earthquake near North Korea's north-eastern nuclear test site, a strong indication that Pyongyang has detonated a fifth atomic test explosion.
South Korea's Joint Chiefs of Staff said in a statement that "artificial seismic waves" measuring 5.0 were detected near the Punggye-ri test site, and officials were analysing whether it was a nuclear test.
European and US monitoring services also detected seismic activity, with the US Geological Survey calling it an "explosion".
North Korea conducted its fourth nuclear test earlier this year, part of a push for a nuclear-armed missile that could one day reach the US mainland.
A second nuclear test this year would be a defiant response to Western pressure on Pyongyang to halt its nuclear ambitions. The country has previously conducted tests every three to four years.
Any new test will lead to a strong push for tougher sanctions at the United Nations and further worsen already abysmal relations between Pyongyang and its neighbours. North Korean nuclear tests worry outside governments because they are seen as moving its scientists and engineers that much closer to the goal of an arsenal of nuclear-tipped missiles that can reach the US.
North Korea is thought to have a handful of rudimentary nuclear bombs and has spent decades trying to perfect a multi-stage, long-range missile to eventually carry smaller versions of the bombs. After several failures, it put its first satellite into space with a long-range rocket launched in December 2012, and has since had another such successful launch.
Experts say ballistic missiles and rockets in satellite launches share similar bodies, engines and other technology. The UN calls the North's long-range rocket launches banned tests of ballistic missile technology.
Some analysts say the North has probably not achieved the technology needed to manufacture a miniaturised nuclear warhead that could fit on a long-range missile capable of hitting the US, but there is a growing debate on how far the North has advanced in its secretive nuclear and missile programmes.