An apparent suicide bomber struck a building housing a government investigative agency Monday in Pakistan's eastern city of Lahore, killing at least 11 people, police and hospitals said.

At least 61 people were wounded in what appeared to be the biggest explosion to strike the nuclear-armed, U.S.-allied country in several weeks.

No group immediately claimed responsibility, but suspicion immediately fell on the Pakistani Taliban and allied militant groups responsible for a wave of attacks that killed more than 600 people late last year — a stretch of violence that appeared to be retaliation for a military offensive against insurgents along the Afghan border.

The explosion went off outside the Federal Investigation Agency building near the perimeter wall, police official Zulfikar Hameed said. TV footage showed a huge crater where the blast seemed to have originated.

Police official Chaudhry Shafiq said it appeared a suicide bomber rammed his explosives-laden car into the perimeter wall.

Hospital official Jawed Akram said the dead included a woman and a young girl. Nine people were in critical condition.

"People are coming with multiple wounds, many with head injuries and broken limbs," he said.

Parts of the brick building appeared to have collapsed, and there were piles of bricks and metal everywhere at the site, the footage showed. Other nearby buildings, including a mosque, also were damaged. Ambulances rushed to the area.

The FIA is a civilian law enforcement agency that has been targeted by militant attacks before, though it appeared to be the first time this particular building had been hit.