An Interior Ministry official says at least 18 people were killed when a suicide car bomber targeted a convoy of provincial security forces in eastern Afghanistan.

Najib Danish, the ministry's deputy spokesman, says the target was a group of guards providing security for U.S. forces in Khost province but most of the victims in Saturday's attack were civilians. No group immediately claimed responsibility.

The convoy of Khost provincial forces was targeted near the province's main bus station, said Danish.

The attack comes on the first day of Ramadan, the Muslim holy month.