A special session of the Assembly had been called to take up a no-confidence vote against Balochistan Chief Minister Sanaullah Zehri but was postponed after he resigned from his post, amid speculation of "horse trading" as the government and the Opposition had claimed to have enjoyed the support of majority of leaders.
The Pakistani Taliban claimed responsibility for the attack, saying a suicide bomber targeted a police contingent returning from duty at the assembly building. He added the primary target of the bomber was police that was why he blew himself up close to their vehicle.
Back in December 2017, a suicide attack on the city's Bethel Memorial Methodist Church left at least nine people dead and 43 others injured.
The incident happened about 300 meters away from provincial assembly building of Balochistan, and the targeted policemen were deployed at the security of the assembly, Samaa News reported.
The security forces cordoned off the area which had already been heavily barricaded.
The injured persons have been shifted to a nearby hospital for immediate medical relief. The local authorities have also declared emergency at hospitals across the city.
A public bus in the area was also damaged in the explosion.
A terrible scene was witnessed as a large number of people were crying in hospitals while searching for their relatives who had either been killed or wounded in the blast.
Inspector General of Police (IGP) Balochistan Moazzam Ansari said that the attack killed four policemen and two civilians.
Security officials said a bomb disposal team was present at the location conducting necessary search and sweep exercise.