A woman clad in a burqa blew herself up at a crowded police checkpoint Monday killing at least 15 people in the northwestern part of the country, Pakistani police said.

The homicide bomber was apparently riding in a rickshaw that was being examined by police. At least 22 others were injured in the blast.

The investigation of the bomb site confirmed that the attacker was a woman, a local police chief said, adding that police had prior intelligence that female bombers might strike the town.

There have been reports in Pakistan of some women being trained to carry out homicide bombings. But Monday's bombing appears to be the first confirmation of such an attack.

The casualty figures were high because there was a crowd at a nearby bus stand, police said.