A suicide bomber on a motorcycle has struck outside a government office in a tribal region where Pakistan's army has fought the Taliban, killing at least 48 people and wounding around 80.
The attack indicated that militants remain a potent force in Pakistan's tribal belt, which borders Afghanistan, despite army offensives.
The US has praised Pakistan for taking on Islamist extremists that use the tribal region to plan attacks on Western troops across the border, but the militants have often retaliated on Pakistani soil.
The bomber detonated his explosives near the Yakaghund village office of a top administrator of the Mohmand tribal region, Rasool Khan.
Khan, who was in his office at the time, escaped unharmed. He said some 70 to 80 shops in the area were damaged or destroyed by the powerful blast. A prison building also was damaged, and some 28 prisoners apparently escaped.
The attacker was on a motorcycle and trying to gain entry to the office when he was stopped and detonated the bomb.
Mohmand is one of several areas in Pakistan's lawless tribal belt where Taliban and al-Qaida are believed to be hiding. The Pakistani army has carried out operations in Mohmand, but it has been unable to totally destroy the militants.