Quetta Police chief Abdur Razak Cheema said auto was detonated by bomb, security forces of vehicle, four policemen on vehicle, and two people who passed road during explosion of vehicle lost ir lives.
Minutes after the blast in Quetta, two security personnel were killed in an IED explosion in the Frontier Region (FR) of Bannu in the country's northwest.
At least nine security personnel and a civilian were killed in separate terror attacks in Pakistan's southwest and northwest on Wednesday.
Balochistan Home Minister Sarfaraz Bugti told the media that fight against terrorism will continue despite the attack. According to hospital staff, the condition of seven injured was critical.
The Pakistani Taliban said the attack was a "suicide mission".
"We are at war and our security forces are being targeted as they are crushing the enemies", Bugti said.
Earlier in June, 14 people - including seven policemen - lost their lives in a suicide blast that shook Shuhada Chowk in Quetta's Gulistan Road area.
He added: "These cowardly attacks will not hinder our security forces in executing their duties".
Security forces have cordoned off the area while BDS personnel are collecting evidence to ascertain exact nature of the blast.
Meanwhile, Prime Minister Shahid Khaqan Abbasi expressed grief on the attack and ordered the authorities to provide best medical treatment on emergency grounds.
Bugti told AFP that a auto rammed the police vehicle before catching fire, adding it was "apparently a suicide attack", in an account confirmed by senior police official Abdul Razzaq Cheema.
Civil Hospital Quetta Spokesperson Wasim Baig confirmed the seven deaths.