The Frontier Corps (FC) personnel were targeted when they were on a routine patrol on Sariab road in Quetta.
Deputy Inspector General (DIG) Quetta Razzaq Cheema said that the attackers fired at the vehicle carrying the FC officials and fled after the incident.
"It was a coordinated attack and the purpose was to target the FC personnel in the vehicle," Cheema said.
"Four security personnel were killed in the attack," he told the media.
This was the latest attack in a series of terror strikes carried out against security personnel in Quetta and other parts of the troubled province this year.
Last month, at least seven persons were killed on Zarghoon Road in Quetta when a suicide bomber rammed his motorbike into a police truck.
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