A senior Pakistani police officer says gunmen shot and killed two paramilitary troops and two workers for an army-owned company at a canal construction site in the country's southwest.

Abdul Ghafoor Afridi says the incident took place Tuesday in the Kolachi area of Dera Ismail Khan district, where the army's construction wing, known as the Frontier Work Organization, is building a canal.

Afridi says the gunmen fled after the shooting and that the motive is not yet known. No group has claimed responsibility for the attack.