A US official says 7 marines have been killed in a training accident in Nevada. Reports say an explosion at an ammunition storage facility caused several fatalities.

Local media is reporting that the blast was unrelated to the ammunition that is kept at the military facility.

A Marine Corps spokesman confirmed that the explosion happened during a training exercise at the Hawthorne army depot in Nevada but would provide no other details.

Separately a military official told AFP on condition of anonymity that there were several casualties.

The depot stores and disposes of ammunition and provides long-term storage for industrial plant equipment.