KABUL, Afghanistan — An Afghan doctor says at least 17 civilians, many of them women and children, have been killed by a suicide car bombing near a U.S. base.

Dr. Hedayatullah Hamedi, the provincial health director of Afghanistan’s Khost province, said the bombing happened Sunday at a checkpoint in the city of Khost.

Hamedi added that out six civilians who are wounded, two are in critical condition.

No group has claimed responsibility for the attack. Youqib Khan, the deputy police chief in Khost province, said the attack happened near Camp Chapman, which still houses U.S. forces.

Pentagon officials referred comment to NATO authorities in Afghanistan. NATO previously said an “explosion” happened in Khost province, without elaborating.