In the first incident, two policemen were on Eid duty when two gunmen on a motorcycle opened fire on them on Saryab road.
SP Zahoor Afridi said the assailants had opened indiscriminate firing on the police mobile in which a constable and a driver were killed on the spot.
In the other incident in the Hazarganj area, unknown assailants opened fire on the vehicle of an SHO and in the retaliatory firing two policemen guarding him were killed.
No group claimed responsibility for the killings. This is not the first time security personnel particularly policemen have been targeted by gunmen in Quetta and in recent months there have been a spate of target killings.