North Korea has been conducting rare mass evacuation and black out drills throughout the country in preparation for war, it emerged this weekend.

Multiple sources told NK News that the drills have taken place in secondary and tertiary cities and towns, particularly along the east coast, but not in the capital city, Pyongyang.

The revelation comes during a time of heightening tensions between the hermit state and the US after a series of nuclear and missile tests, including an intercontinental ballistic missile (ICBM) capable of striking mainland America.

The threat of nuclear missile attack by North Korea is accelerating, US Defence Secretary James Mattis said on Saturday during a trip to the South Korean capital, Seoul, to meet his counterpart, Defence Minister Song Young-moo.

“North Korea has accelerated the threat that it poses to its neighbours and the world through its illegal and unnecessary missile and weapons programmes,” he said, adding that US-South Korean military and diplomatic collaboration had taken on “a new urgency.”

Mr Mattis warned that the US would never accept a nuclear north and that dictator Kim Jong-un was overmatched by American firepower.