The bomb was packed in an oil canister and placed outside the shop, local police officer Javed Khan said.

"The blast left 13 people wounded, one of them seriously," he said, adding that it also damaged two shops and one vehicle parked nearby.

The wounded were labourers or passersby, the policeman said.

The chief of the local bomb disposal squad, Shafqat Malik, said it was a home-made timed device. It carried about three to four kilos (6.5 to nine pounds) of explosives, he said.

The target seemed to be the grocery shop, senior police officer Tahir Ayub told AFP.

"We are investigating why this shop was targeted," he said. There was no immediate claim of responsibility.