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Reports have emerged the nuclear test range was hit by a double tunnel collapse following Pyongyang’s detonation of an H-bomb.

The tunnel was “unfinished” and was being constructed at the mountain site Punggye-ri.

At least 100 workers excavating the new dig were crushed, and another 100 were killed in a second collapse during rescue efforts, reports Japanese TV.

North Korea observers have made repeated warnings about the risk of collapse following a number of inexplicable earthquakes.

Fears have also been raised that a major incident could release massive amounts of radiation over the Korean Peninsula.

Chief of South Korea's weather agency Nam Jae-cheol warned another nuclear blast could trigger a collapse of the North's mountainous test site.

North Korea tested its biggest ever nuclear bomb back in September, a weapon five times more powerful than the bomb dropped on Hiroshima.

Since then, geologists have been detecting tremors at the test range – suggesting it was unstable and could face disaster.

The collapse revealed today is believed to have occured on September 10 – seven days after the H-bomb test.

(Image: GOOGLE) (Image: GETTY)

Punggye-ri is North Korea’s only known nuclear test site – and is located in the Northern region of country near their borders with Russia and China.

The rogue state has carried out six nuclear blasts in tunnels dug beneath the mountain range.

Satellite images often show huge mounds of dirt near the base, which suggest activity related to nuclear tests.

Previously, Paul Richards, a seismologist at Columbia University's Lamont-Doherty Earth Observatory, said: “What we are seeing from North Korea looks like some kind of stress in the ground.

"In that part of the world, there were stresses in the ground, but the explosions have shaken them up.”

Reportedly people from Punggye-ri are banned from entering Pyongyang due to radioactive leaks around the site.

(Image: GETTY)

Tensions continue to rage between the West and North Korea over Kim’s quest for nuclear ICBMs.

Pyongyang has been silent since September 15 – not carrying out any nuclear or missile tests since firing one over Japan.There are now fears Kim could make good on his threat to fire the dreaded "Juche Bird".