N. Korea threatens U.S. of 'unimaginable' nuclear strike

North Korea has threatened the United States of an "unimaginable" nuclear strike for conducting military exercises with South Korea in the waters off the Korean peninsula.

"The United States is running amok by introducing under our nose the targets we have set as primary ones," a state-controlled Korean Central News Agency warned, reports the New York Post.

"The U.S. should expect that it would face an unimaginable strike at an unimaginable time," it added.

The regime also blamed the United States for "creating tension on the eve of war" by taking part in civilian evacuation drills in South Korea.

Earlier on Monday, the United States and South Korea military forces began five days of military exercises that involve fighter jets, helicopters and about 40 ships and submarines.

North Korean leader Kim Jong Un Government considers the drills a rehearsal for an invasion of his country.

Tensions have increased between Pyongyang and Washington since the regime began testing intercontinental ballistic missiles that could hit the U.S. mainland.

It also detonated a nuclear device.

The United Nations (UN) has imposed strict economic sanctions against the country in retaliation for continuing its weapons development program.

United States President Donald Trump has said he would 'totally destroy' North Korea in defense of the U.S. or its allies.