However, the nature of the blast has yet to be ascertained.
According to reports, a 35-strong contingent of Elite policemen had been recently assigned patrol of various sensitive areas and was on its way when the explosion took place on the Quetta-Sibi road, Balochistan Home Minister Mir Sarfraz Bugti said, adding that it was "apparently a suicide attack".
Rescue teams shifted the injured persons have been shifted to the Civil Hospital for treatment.
Police and FC troops have reached the area, which has been cordoned off for gathering evidence.
No group had claimed responsibility for the auto bombing.
The minister said that 21 others were injured in the attack on Sariab Road near Darakhshan Railway Phaatak, while a police official put the number of wounded at 25.
The police sources say that it was a suicide attack.
Modi Shares The Stage With Bihar CM Nitish Kumar At Patna Univ
While addressing the event, Nitish Kumar demanded that the Patna University should be given the status of a Central University. Closer to the time that PM Modi's fight was to land, he was moving towards the tarmac when the incident took place.
"We can not yet say that this is a suicide attack, our teams are in research and investigations at scene", Cheema said.
"The war against terrorism is not over".
Violence has declined in Pakistan after the army conducted a series of offensives against Islamist militants since 2014, however the groups still possess the capability to launch surprise attacks on security forces and civilian targets.
"Balochistan is on the forefront of this fight and we will not stop until there is not a single terrorist left in the area", he added.
Later in the day, unidentified gunmen shot dead CTD Police Inspector Abdul Salam at Qambrani Road of the provincial capital, said police.
Fifteen people, including eight soldiers, were killed when a suicide bomber targeted a military truck near the Pishin bus stop in Quetta on August 13.
Strongly condemn terror attack in Quetta causing loss of precious lives.