Five policemen were killed on Tuesday when unidentified militants opened fire on a police vehicle in Pakistan's northwestern Khyber Pakhtunkhwa province, police said.

The incident took place at around 8:45 am local time in Karak district. The sources, speaking on condition of anonymity, told Xinhua that the attackers opened fire on the vehicle.

The police immediately returned fire, and the clash lasted for about an hour.

All five police personnel in the vehicle were killed in the gunfight, the source said. The militants also set fire to a police vehicle before fleeing the scene after the attack. No group has claimed responsibility for the attack yet.