North Korea has denied reports of a tunnel collapse at the Punggye-ri nuclear test site facility, slamming them as "false" news reports. Pyongyang said the allegation was part of a large conspiracy by the Japanese forces to invade North Korea under the pretext of a nuclear threat.

It was earlier aired by Japan's TV Asahi that up to 200 people were killed when a tunnel at Punggye-ri, where the North had conducted six nuclear tests since 2006, had crumbled on workers. However, the media outlet did not provide more details on how or when the collapse occurred. There was no independent confirmation of the collapse as well.

Responding to the report, North Korean state mouthpiece carried a dispatch, condemning the Japanese broadcaster.

"The controversial report about misinformation is also part of the Japanese reactionaries' clumsy trick to divert elsewhere the heated-up public attention," read a statement carried by the reclusive nation's Korean Central News Agency (KCNA).

"Several media openly complain, branding the Japanese reactionaries' moves to render the fictitious story about 'threat from the north' extremely serious as a frivolous act peculiar to Japan aimed to justify their arms build-up," added the KCNA dispatch.

It is nearly impossible to verify such reports from North Korea as the hermit kingdom does not permit outside media outlets to operate inside the country.

Following the North's sixth and most powerful nuclear detonation on 3 September, there have been serious concerns over the stability of the mountainous underground test site and about possible radiation leaks. Experts have cautioned that Punggye-ri could collapse if another nuclear test blast is carried out by the regime in the same site.

North Korea nuclear test
DigitalGlobe satellite image of the Punggye-ni Nuclear Test Facility in North Korea