Two U.S. service members have been killed in an explosion in southern Afghanistan, NATO says.

Lt. Col. Todd Vician says the two were killed by a bomb explosion in Zabul province late Thursday morning. He did not have any further details.

Jilani Farahe, deputy chief of police for the province, said a suicide car bomber detonated his explosives near the gate of a NATO base. He said no civilians had been hurt in the blast.