DIG Wazir Khan Nasir was reported by a foreign news agency as saying that all the dead belonged to Hazara community and the death toll might rise.
A large number of women and children are among the victims of the mega blast that hit Qutta on Saturday.
Earlier CCPO Quetta said 63 people were killed and 180 others injured in the blast, however the toll ticked up to 79 later.
He said the Improvised Explosive Device (IED) the terrorists planted in a watertank was armed with around 800-1000 kilograms of high-grade detonable material.
He said people with critical injuries would be flown to Karachi through military aircraft C-130.
The officer said an official day of mourning would be observed over the incident in Balochistan on Sunday.
According to reports the explosion demolished several markets in the area.
More casualties were feared as many of the injured were in critical condition.
Adjacent areas reverberated with intense firing following the blast while heavy contingent of police and Frontier Corps (FC) rushed to the spot and cordoned off the area.They were not allowing people including media men to reach the spot.
Rescue sources said plumes of smoke were seen shortly after the huge blast. Many vehicles were also damaged due to the blast.Enraged people took to the streets and protested the blast, pelting vehciles with stones and blocking roads. Most of the people were busy in shopping as the blast hit market.
Initial reports said four people were killed while many others injured. However, Geo News correspondent says death toll started climbing as victims succumbed to their wounds in hospitals where a state of emergency was declared. He says the blast occurred in a bazaar located near a densely populated area.
The dead and injured were taken to the Civil Hospital and Bolan Medical Complex. Police also confirmed the blast. However, nature of the blast and identities of the victims were yet to be ascertained.
Various religious and political parties have announced to mark day of mourning over the tragic incident.