At least nine people have been killed after a bomb exploded in a crowded market in northwestern Pakistan.

The blast in Salarzai town in the Bajaur tribal area also wounded over a dozen people, some of them critically, said Jehangir Azam, a local government administrator.

Twenty others were wounded when the device, planted in a pick-up truck, exploded in Pasht bazaar of Salarzai.

"There are nine bodies and 20 wounded brought to hospital," Doctor Khalilur Rehman told the AFP news agency.

Two children aged eight and 13 were among the dead and four children aged five to 11 were among the injured, he said.

No group has claimed responsibility for the attack.

PHOTO CAPTION

A paramilitary soldier walks on site to request the media move to away from the site as policemen survey the area after a bomb attack in Karachi July 23, 2012.

Al-Jazeera