At least 17 people have been killed as a suicide car bomber rammed a heavily fortified police station in north-west Pakistan, officials have said.
Up to 20 others were injured as the explosives-laden Toyota Stout caused a huge blast at the Merian police station in Bannu district.
Witnesses said parts of the building and a mosque inside the compound have collapsed.
The Pakistani Taliban said they carried out the attack to avenge drone raids.
Bannu is close to Pakistan's troubled tribal areas which border Afghanistan.
Plunged into darkness
Police told the BBC the car bomber had rammed the outer wall of the Merian police station, which is in a densely populated area.
They said more than 50 police officers were in the station at the time of the attack.
The official Pakistan Television Corporation reports that all the dead were members of the Frontier Corps, a federal paramilitary police force.
Witnesses say the district was plunged into darkness by the blast as electricity lines were damaged.
The station is 12km (seven miles) south-west of Bannu town, near the border with Janikhel tribal area, which serves as a buffer between Bannu district and the North Waziristan tribal region.
"We claim responsibility for this attack. We will continue such attacks unless the drone attacks are stopped," a Taliban spokesman, Azam Tariq, told AFP news agency by telephone.
He was referring to the missile raids by unmanned US aircraft which have killed hundreds of militants and civilians.
The drones target tribal areas along the border with Afghanistan, a region known as a sanctuary for the Taliban and al-Qaeda.
Militants have killed hundreds of people in a wave of attacks in recent years in Pakistan. Police and army personnel have frequently been targeted.
Wednesday's blast came as Vice-President Joe Biden visited the Pakistani capital Islamabad and denied Washington had imposed a war on terror on Pakistan.
"We are not the enemies of Islam and we embrace those who practice that great religion in our country," he said in a joint news conference with Pakistani Prime Minister Yousuf Raza Gilani, reported by the AP news agency.
On Wednesday morning at least three militants died in a US drone strike in north-west Pakistan. Four missiles struck a compound near Mir Ali town in North Waziristan.