The three men were travelling in a Pajero wagon when men on motorcycles opened fire on them on Prince road, police said.
"Some passers-by were injured in the firing while the three men died when they were being taken to hospital for treatment," a police official said.
The official declined to give the identity of the men killed but one of them was reportedly the son of a tribal chief in the Balochistan province.
Meanwhile, in Karachi a minor explosion injured two personnel of the paramilitary Rangers in the Manghopir area.
"Two personnel were injured in the blast but they are out of danger now," an official said.