Moulvi Mohibullah, his brother and a colleague were sitting at a shop on Khudadad Road late last night when armed men riding a motorcycle fired at them indiscriminately, police said.
They were killed instantly and three other persons sustained bullet wounds. Rescue teams took the dead and injured to the Civil Hospital.
Later, some of the injured were shifted to a military hospital. No group claimed responsibility for the attack.
The incident occurred hours after four Shia Hazaras were shot and killed in Quetta, the capital of the restive Balochistan province.