North Korea said it has successfully conducted a solid-fuel, high-powered rocket engine test in a move that the country's leader says will boost missile attack capability, the Associated Press reports.

North Korea is known to use liquid propellants for its main ballistic missiles that target South Korea, U.S. bases in the Asia-Pacific region and the American mainland.

Liquid-fuel missiles need to be re-fueled each time before they are launched, so it's difficult to use them on short notice. The use of solid propellants reduces launch preparation time and increases the mobility of the missiles, making it harder to detect signs of firing.

The North's state media Wednesday, March 23, quoted leader Kim Jong Un as saying the test will enhance a missile capability that "mercilessly" strikes enemies.

The AP says the claims could not be independently confirmed.