North Korea says it test-fired a ballistic missile fitted with a mock nuclear warhead on Sunday morning as part of a drill simulating a tactical nuclear counterattack.

The ruling Workers' Party newspaper, Rodong Sinmun, reported on Monday that a tactical ballistic missile was launched from the northwestern province of North Phyongan toward the sea off its east coast.

The newspaper reports that the drill included the procedures for the final nuclear attack order and for switching to a nuclear attack posture.

It also reports that the missile carrying a mock nuclear warhead accurately exploded at 800 meters above the target waters in its 800-kilometer strike range, proving the reliability of detonators.

The test apparently refers to the missile launch reported by the South Korean military on Sunday. The military said the North fired a short-range ballistic missile from North Phyongan Province toward the Sea of Japan.

North Korean leader Kim Jong Un observed the drill with his daughter.

Kim reportedly said a nuclear attack that can be conducted quickly and accurately at any time is a means to actually attack the enemy. He added that the country can only fulfill the important strategic mission of deterring war when it is fully prepared.

North Korea launched its latest missile amid the ongoing joint military drills by the United States and South Korea.