Two U.S. service members were killed early Saturday, Sept 12, during a "sustained attack" at a joint base in southern Afghanistan's Helmand province, military officials said, according to CNN.

The slain Americans were both Marines, a U.S. defense official said, while three or four troops were wounded.

The Taliban claimed responsibility.

Between 16 and 20 insurgents were killed, said Jamie Graybeal, a spokesman for the International Security Assistance Force. Attackers used a combination of small firearms and rocket-propelled grenades in their attack, according to the official.

They may have breached the "outer perimeter" of the base - which includes the American-run Camp Leatherneck and the British-run Camp Bastion - added the official.

Maj. Martin Crighton, a spokesman for the International Security Assistance Force, said the base came under indirect fire.

He said there were no organized demonstrations outside its gates - as have sprung up worldwide in recent days, targeting U.S. authorities following the release of a privately produced anti-Islam video - prior to the attack. A Taliban spokesman said the attack was in response to the film.