A Frontier Corps personnel and a 13-year-old child were among those killed by the blast at Satellite Town in Quetta, DIG (Operations) Mohammad Jaffar told reporters.
Nine security personnel were among the injured.
"Unknown men fitted a remote-controlled device to a bicycle and parked it near the vehicles of security forces. They exploded it as security men were busy checking vehicles and pedestrians," Jaffar said.
Nearby buildings were damaged by the blast. The victims were taken to Quetta Civil Hospital.