At least 200 North Korean labourers had been reportedly killed after a mine shaft which is being dug at a nuclear test site collapsed, the Telegraph reported today quoting Asahi TV.
Sources in North Korea had told the news channel that a tunnel being excavated by around 100 workers at the Punggye-ri test site collapsed earlier this month.
An additional 100 labourers who were sent to rescue trapped labourers had also been reportedly killed when the tunnel suffered a second collapse.
An exact date for the disaster has not been provided, but it comes shortly after North Korea conducted its sixth - and most powerful - underground nuclear test at the site.
North Korea claims the September 3 test beneath Mount Mantap was of a hydrogen bomb, with monitors suggesting the detonation was equivalent to an earthquake with a magnitude of 6.1 on the Richter scale.
Some analysts put the yield of the weapon as high as 280 kilotons, while seismologists picked up signs of underground collapses in the hours and days after the blast.
Satellite images of the Punngye-ri site taken immediately after the test revealed significant damage to surface features, including landslips.