? ISLAMABAD, Feb. 12 (Xinhua) -- At least four policemen were killed in an ambush in Dera Ismail Khan district of Pakistan's northwest Khyber Pakhtunkhwa province on Tuesday, local media reported.

The militants opened fire at the police vehicle, and fled the scene, Dawn News said, adding that the law enforcement agency has kicked off a search operation in the area after the incident.

The police vehicle was on its routine patrolling in the city when it was attacked by the insurgents.

Two passersby got injured in the attack and were shifted to a nearby hospital.

No group or individual has claimed responsibility for the attack yet.