A mortar explosion at a US army munitions depot in Nevada killed seven marines, and injured eight others during a live-fire training exercise.

A Marine Corps official said a 60mm mortar round exploded prematurely during training at the Hawthorne Army Depot in western Nevada.

Seven marines from Camp Lejeune in North Carolina were killed.

They had been undergoing training for the past month at the Marine Corps Mountain Warfare Training Center in Bridgeport, California, and at Hawthorne.

The blast was among the deadliest such training accidents on US soil in recent years.

In February, seven marines were killed when two helicopters collided during an exercise along the California-Arizona border.

The Marines Corps has ordered a blanket suspension of the use of 60mm mortars pending a review of the explosion on Monday night.