The blast took place in a parking lot near Pishin bus stop which is in a high security area.
Baluchistan's Home Minister Mir Sarfaraz Bugti said the bomb was apparently kept in a vehicle parked near the bus stop.
"Investigations are continuing but I can confirm it was a big explosion and there are around two dozen injured who are being shifted to nearby hospitals," Bugti said.
Twelve dead bodies were brought to the hospital and they were all badly charred and burnt, Duniya channel reported.