Pakistani police say a powerful suicide car bomb has rocked the eastern city of Lahore, killing at least 13 people and wounding 70.
Hospital officials say a woman and a child were among those killed in the attack.
The Monday morning rush-hour explosion collapsed the two-story building housing the Federal Investigation Agency, damaged several nearby buildings and left a large, gaping crater. Authorities estimate as much as 600 kilograms of explosives was used in the attack.
Pakistan's Taliban claimed responsibility for the attack on the police investigation offices. Taliban spokesman Azam Tariq says it was to avenge U.S. drone attacks and Pakistani military operations in the tribal areas near the Afghan border.
Meanwhile, Pakistani intelligence officials say five people were killed Monday in suspected U.S. drone attacks in the North Waziristan tribal region.
Officials say at least one other person was injured in the strike, which targeted a suspected militant compound in Miran Shah, the main town of North Waziristan.
The U.S. embassy in Pakistan strongly condemned the attack in Lahore. An embassy statement says such "brutal acts" illustrate a terrorist agenda of "fear and intimidation."
The attack broke what had been a relative lull in major violence in Pakistani cities.