Khost: A suicide car bomb on Sunday killed 33 people and wounded 10 in southeastern Afghanistan, close to a U.S. base that was once used by the CIA, police said.

The attack took place close to a checkpoint on the outskirts of the city of Khost where several cars had been stopped, the provincial police chief, Faizullah Ghairat, said.

At least 12 of those killed were children, according to the United Nations, and most of the casualties were civilians.

The U.S. military said none of its personnel were hurt, but declined to give details of the size of the contingent at the base in Khost province.

The base at Camp Chapman was once used by the CIA to help oversee strikes against militants and it was unclear if the intelligence agency still operated there.

Camp Chapman suffered one of the worst attacks in CIA history in late 2009, when seven intelligence officers were killed by an al Qaeda operative whom the Americans thought had been "de-radicalised".