An official says gunmen in eastern Afghanistan have opened fire on highway, killing at least 13 people in passing vehicles.

Attahullah Khogyani, a spokesman for the provincial governor of Wardak province, said Tuesday that the gunmen shot at three vehicles, including a bus from Kabul to heading to Ghazni province.

He said two other civilians were wounded in the attack, which took place after midnight in Wardak province's Sayad Abad district.

No group immediately claimed responsibility for the assault. Most areas of Sayed Abad district are under the control of the Taliban, whose fighters often plant roadside bombs and launch other attacks on passing security convoys.