Three Frontier Corps personnel were gunned down in Quetta's Sabzal Road area on Friday.
According to police sources, suspected militants opened fire at the FC men. Two men died on the spot, whereas the third succumbed to his injuries on the way to the hospital. The bodies were shifted to a nearby hospital.
The attackers escaped unharmed.
Police and a large contingent of FC arrived at the spot shortly after the incident and investigations into the attack have started.
There has been no claim of responsibility for the attack.