Police officials said two Hazara Shia men were standing outside a passport office on Joint Road when gunmen riding motorcycles fired at them.
The two men sustained multiple bullet wounds and died while being taken to hospital, officials said.
The dead men were brothers.
A passerby was injured in the attack and the gunmen managed to escape from the scene, they said.
No group has claimed responsibility for the attack though similar incidents in the recent past have been blamed on the banned Lashkar-e-Jhangvi.
Law enforcement personnel cordoned off the area and launched a search to trace the attackers.
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Officials said a preliminary investigation indicated that the shooting was an incident of sectarian violence.
Dozens of members of the Hazara Shia community have been killed in targeted attacks in Quetta, the capital of Balochistan province, and nearby areas this year.