A car bomb targeting security forced has exploded at a market in northwest Pakistan, killing at least 11 people and wounding more than 40 others, officials say.

The blast struck near a convoy of security forces in Parachinar town of Kurram district, senior administration official Sahibzada Mohammad Anis said. 

The death toll is expected to climb..

"The death toll is 11," Anis said, updating the earlier figure of 10. There are more than 40 wounded, 20 of them are in serious condition, he added.

The blast also destroyed 30 shops and damaged 50 others in the busy commercial area, Anis said, adding that the site was littered with rubble, concrete slabs, and twisted metal.

There was no immediate claim of responsibility for the blast, but the Pakistani Taliban have staged similar attacks.

"A large number of people were present in the market when the blast took place," tribesman Dildar Hussain told the Reuters news agency by telephone.

"Most of those killed and injured were the poor people selling vegetable and fresh fruits on their push-carts."

He said the explosives were planted in a vehicle loaded with grapes.

Suicide bombings have eased over the last year but it's not clear if that is due to pressure from the army or a shift in Taliban tactics.

Source: Agencies