Civilians are reported to be among at least 10 people injured in the bombing.

Senior police official Liaquat Ali said the attacker had rammed his car into a police vehicle.

The blast highlights the ongoing threat of militancy despite army offensives in tribal regions along the border to flush out Taliban and al-Qaeda havens.

"The vehicle was coming from the tribal area. It was full of explosives," Mr. Ali told the news agency AFP by telephone.

No group has admitted attack on April 28, but the Taliban have carried out dozens of recent bombings.

Hundreds of people have been killed in militant attacks across Pakistan since the military launched operations against the Taliban last autumn. Peshawar has borne the brunt of this violence.