The police officials in Quetta have confirmed the incident and said at least 31 people including policemen and civilians lost their lives in the attack.
The officials further added that the attack also left more than 20 people wounded with at least eight of them in critical condition.
The Inspector General Police Quetta Mohsin Butt confirmed that an explosion, apparently triggered by a suicide attack, targeted a police vehicle.
He said investigations are underway regarding the incident but has not elaborated further in this regard.
No individual or group has so far claimed responsibility behind the attack.
This comes as the country witnessed violence during the election campaigns that claimed the lives of scores of people.
The Pakistani Taliban group and the ISIS loyalists claimed responsibilities for the recent string of attacks in Khyber Pakhtunkhwa and Balochistan provinces of Pakistan.
Today’s incident takes place as millions of people have gone to the voting centers to vote for the candidates who are competing for 272 seats in the Provincial Assembly.