As many as 200 North Koreans have died due to the collapse of a tunnel after nuclear testing

The collapse of a tunnel under construction near the North Korean nuclear complex would have killed more than 200 workers, media reports said.

About 100 people died after the collapse of a tunnel under construction near the North Korean nuclear site of Punggye-ri. According to the Yonhap agency, the tunnel was very fragile after North Korea's last nuclear test on 3 September.

According to the Japanese television station Asahi, a second collapse in the same tunnel happened later, when rescue operations were under way, increasing the number of victims to 200 people.

The Japanese television channel gave no further details. The exact dates of the incidents are not known.

Experts had warned that the Punggye-ri nuclear zone had become unstable after Pyongyang's six nuclear tests and that a collapse could happen at any time.

On October 30, Nam Jae-cheol, head of the South Korean Meteorological Administration, said in an interview with Yonhap that if North Korea detonated another nuclear device, it could trigger a collapse of the mountain next to the polygon and also a leak of radioactive materials.