Seven people were killed and 21 wounded in a homicide car bomb attack in the northwestern Pakistani city of Kohat on Sunday, police said.

"It was a suicide attack, the target was a police station," Dilawar Khan Bangash, city police chief, said. "The bomber exploded his vehicle an the back side of the police station."

Abdullah Jan, the district's top police officer, said: "Seven people have been killed and 21 were injured in this car homicide attack.

"These incidents are a reaction to the military operation in the tribal areas."

Another senior police officer confirmed the attack, adding that around 440 pounds of explosives were used.

The attack comes just a day after two homicide bombers dressed in burqas struck a crowd of displaced people collecting aid handouts, killing at least 41 and wounding more than 60 at a nearby camp.

The bombers struck minutes apart on Saturday in the Kacha Pukha camp on the outskirts of the garrison city of Kohat, a registration center for people fleeing Taliban violence and Pakistani army operations close to the Afghan border.