The militants planted roadside bombs on the Quetta-Chaman highway near Pishin and detonated two explosive devices when a police patrol vehicle was passing the area.
District police chief Mahboob Rasheed told PTI that five persons, including four policemen, were killed by the intense blasts.
The injured were taken to the Civil Hospital in the provincial capital of Quetta, he said. Pishin is located 50 km from Quetta.
Baloch nationalist groups and Islamist militants have intensified attacks in the troubled province since last year. They have mainly targeted government and security installations and security personnel.