The Frontier Corps (FC) personnel were targeted in Quetta when they were on a routine patrol.
Deputy Inspector General (DIG) Quetta Razzaq Cheema said that the attackers fired at the vehicle carrying the FC officials and fled after the incident.
“Four security personnel were killed in the attack,” Cheema said.
No one has claimed responsibility for the attack but Baloch nationalists and Taliban militants often target security men in the province.
At least seven persons were killed on Zarghoon Road in Quetta last month when a suicide bomber rammed his motorbike into a police truck.
Balochistan Governor Mohammad Achakzai condemned that the latest attack and urged the law enforcement agencies to arrest the culprits at the earliest.