A burqa-clad suicide bomber set off a blast that killed at least 15 people Monday at a crowded police checkpoint in northwestern Pakistan, police said.
The bomb, which injured 22 others, apparently was in a rickshaw that was being examined at a police checkpoint around 8:25 a.m. local time in the town of Bannu, said police officer Habib Khan.
He said initial investigations suggested the blast was detonated by a passenger in the rickshaw who was wearing a burqa, an all-encompassing outer garment worn by women. It wasn't immediately confirmed that the bomber was a female, but police said early evidence collected at the scene suggested this.
"We have confirmed that the passenger sitting in the rickshaw was wearing a burqa and detonated the bomb, but we are checking whether the suicide bomber in a burqa was a man or a woman," Interior Minister spokesman Javed Iqbal Cheema said.
While there have been reports of some women being trained to carry out suicide bombings in Pakistan, it was not immediately clear if any have ever undertaken such an attack.
Bannu police chief Ameer Haamza Mahsud said the casualty figures were high because scores of people were milling about at a nearby bus stand.
The blast killed four police officers and 11 other people, including the bomber, army spokesman Maj. Gen Waheed Arshad said. Because the attack occurred in a public place, he said he did not believe it was aimed at security forces.
The district hospital in Bannu reported that at least seven of the injured were in critical condition.
Bannu is near the North Waziristan tribal region, about 110 miles south of Peshawar.
In recent months, militants have staged almost daily attacks on security forces in North Waziristan since scrapping a peace agreement with the government.
Militants accused authorities of violating the September 2006 deal by redeploying troops to checkpoints vacated under terms of the accord. Officials said the troops returned because of deteriorating security. Most of the combat has taken place in the rugged mountains along the Afghan border where the U.S. fears al-Qaida is regrouping and that Osama bin Laden is hiding.
Pakistan is a key ally of the U.S. in its war on terror and says it has about 90,000 troops in the northwest tribal areas to combat militancy and prevent infiltration into neighboring Afghanistan.