Pakistani police say a homicide car bomber has killed seven people in the northwestern town of Bannu.

Bannu police chief Mohammed Alam Shinwari said the attacker rammed an explosives-laden vehicle into a police car patrolling the town's streets on Friday.

Shinwari said four police officers and three civilians died and several other people were wounded.

Islamic militants have responded to Pakistani military operations and U.S. missile strikes in their strongholds along the Afghan border with a string of homicide blasts.