The Shia men, who belonged to Hazara community, were killed after unknown gunmen opened fire at their motorcycle on Brewary road near Sardar Bhadur Khan Women University in Quetta on Saturday, Press TV reported.
The assailants escaped from the scene after the attack.
Security forces transferred the bodies of the men to a local hospital after the incident.
The relatives of the victims and large group of Hazara community reached the hospital and started protesting against the killing.
In another incident, Pakistani police forces recovered two dead bodies from Kuchlak area of Quetta on the same day.
Police have started an investigation and registered a case against the unknown gunmen.
The killing of Shias has caused international outrage, with rights groups and regional countries, including Iran, expressing concern over the ongoing genocide.