A car bomb attack on a mosque near a police compound in north-western Pakistan has killed at least 16 people, with some officials putting the death toll at 21, and left more than 100 injured.

The attack took place in the city of Kohat, in Khyber Pakhtunkhwa province, around 13:15 local time (08:15 GMT) on Friday, while prayers were under way.

According to reports, an explosives-laden vehicle rammed the gate of the police complex before detonating. The blast was followed by gunfire and, according to some accounts, a second suicide explosion.

Among those killed were 15 police officers and a four-year-old child, according to Pakistan's state news agency. Khyber Pakhtunkhwa police Inspector General Zulfikar Hameed described the incident as a "suicide attack." All seven attackers were reported killed in the explosion and the gun battle that followed.

No group has claimed responsibility for the attack.

A clearance operation was under way at the site following the assault. Video from the scene showed the area covered in rubble, with people tending to casualties.

Pakistan's President Asif Ali Zardari expressed "his best wishes for the swift recovery of those injured in the explosion." Prime Minister Muhammad Shehbaz Sharif also condemned the attack.

Militancy in Pakistan's border areas has risen sharply in recent months, with armed groups increasingly targeting military and police personnel.

The Pakistani government has said militants use Afghanistan as a safe haven to train and plan attacks inside Pakistan. Afghanistan's Taliban government denies the accusation, saying militant groups are a domestic problem for Pakistan.