Preparing for attack: Massive mock terror drill involving 70,000 American and South Korea troops underway over fears of war with Kim Jong-Un

Dramatic images show armed South Korean forces playing out a mock terror drill brandishing guns and wearing biohazard suits in preparation for any North Korean nuclear strike.

The computer-simulated military exercises came as North Korea warned of a "uncontrollable nuclear war" with the US as 70,000 American and South Korean troops began the exercise today.

Images from near Seoul have revealed South Korean soldiers and emergency services wearing protective gear in exercises as they appear to encounter "dangerous substances".

In one exercise in Goyang, north of the capital, South Korean combat policemen were shown facing "terrorists" with guns standing over people crouching on the ground with their hands over their heads.

Explosions went off as heavily armed special SWAT-style teams ordered people around and climbed down the sides of buildings by rope.