A policeman was killed when some unknown militants opened fire at him in Pakistan's northwestern Khyber Pakhtunkhwa province, police said on Monday.

The incident happened in Dera Ismail Khan district of the province on Sunday night when the militants ambushed the policeman's vehicle on his way home from work, the district's police said in a statement.

The attackers fled the scene after the incident, and a probe is being made to trace their whereabouts.

No group has claimed responsibility for the attack yet.

Earlier last week, a group of well-equipped militants attacked an oil drilling company's plant in Dera Ismail Khan district, causing the death of two policemen with three other people injured.

(With UNI Inputs)