PESHAWAR: A suicide bomber blew up his explosives-filled car Saturday at a police checkpoint in the northwestern Pakistani city of Peshawar, killing at least seven people, officials said.

"At least seven people have been killed and more than 20 others wounded," Peshawar police chief Liaqat Ali Khan told AFP.

"There are two policemen among the dead," Khan said.

Peshawar district administration chief Sahibzada Anis said that the bomber detonated when policemen asked him to stop for the search.

"A suicide bomber exploded his car when police tried to search his car at a checkpoint at a big crossing at the outskirts of Peshawar," Anis said.

Senior police official Mohammad Alim Shinwari also said that it was a suicide bombing.

Live television footage showed a huge cloud of smoke above the Pushta Khara neighbourhood of Peshawar and the wreckage of several cars.

Peshawar, on the edge of Pakistan's tribal belt infested with Al-Qaeda and Taliban fighters, has increasingly become the favoured target for attacks by militants, particularly since the army launched its offensive in October.

Early Friday a suicide attack in the city of Peshawar devastated the three-storey provincial headquarters of Inter Services Intelligence (ISI), which is heavily involved in Pakistan's anti-terror fight.

At least 17 people were killed and 39 others were injured in the bombing, officials said. Taliban militants claimed responsibility.

The most devastating bomb attack in Pakistan in two years killed at least 118 people in a crowded Peshawar market on October 28 as militants put ordinary civilians in the crosshairs of their bloody campaign.

Friday's bombing was the first major attack outside an ISI installation since May, when a suicide attack on a police building in the city of Lahore killed 24 people.

The government blames increasing attacks on Tehreek-e-Taliban Pakistan (TTP), which is the target of the ongoing offensive and which wants to avenge the killing of their leader Baitullah Mehsud by a US missile in August.