There were angry demonstrations after the killings of the Shia, in what police described as the latest sectarian attack in the volatile southwest province.
The gunmen, who were on a motorbike, fired at a van carrying members of the minority Muslim community in the Speeni Road neighbourhood of Quetta city, Baluchistan, police official Jamil Kakar told AFP.
"Four people including a woman were killed and seven others were wounded," Kakar said, adding that it appeared to be a sectarian attack.