Police said the bomb was planted in a motorcycle parked outside a restaurant at city’s busy Prince Road and was detonated through remote control.
Nadeem Kausar, an eyewitness, told the Anadolu Agency that at least 30 injured had been evacuated to the hospital.
“It was a massive blast. I was at least 300 meters away from the site but the intensity of the blast was as huge as many, including me, fell on the ground,” Kausar said.
The blast smashed the windowpanes of adjoining buildings and damaged several cars and motorcycles parked along the road. Sidewalks on either sides of the road were strewn with broken glass, shoes, torn pieces of clothes, caps, and other belongings of the injured.
No group has claimed responsibility for the attack; however, secular Baluch separatists or Taliban militants recently have been involved in such attacks.
Quetta has been born the dual threat of the Baluch separatist movement and Taliban militancy, coupled with sectarian violence, for decades.
Government forces have been facing a fierce rebellion in Baluchistan for decades in the area, which is rich in copper, gold and natural gas.
Baluch separatists who have been fighting for the "liberation" of Baluchistan claim that the mineral-rich province had forcibly been incorporated into Pakistan at the time of partition of united India in August 1947. The province has witnessed various spates of insurgency from Baluch separatists with short and long intervals in last 66 years.