“The result and significance of this test will be a source of excruciating mental agony and serious threat to the forces that attempt to provoke a military confrontation with us,” Kim said.

While acknowledging that development of the rocket launcher system had “not been plain sailing”, Kim said the test was “of great significance in improving the effectiveness of our strategic deterrent”.

Photos released by state media showed Kim and his daughter, who analysts believe is called Ju Ae, watching the missile launch.

The rockets “hit a target” in waters 358.5 kilometres (222.7 miles) away, according to the North Korean leader.