The governor of the Nimroz province, where the attack occurred, Ghula Dastagir Azad said two police officers were among the dead, adding that the death toll could rise.
People were attending evening prayers in Zarang city, the capital of Nimroz province, at the time of the blast. Some of them have been hospitalized in a critical condition, Azaad added.
The official also said it seemed the attack might have been carried out by "more than one bomber."
No group has yet claimed responsibility for Thursday's attack.