Superintendent of Police Imran Qureshi said the militants had planted explosives in a motorcycle parked near a Nadra office in the crowded Double road area of the city.
“Two people died on the spot,” Qureshi said.
The intensity of the blast smashed glass windows of nearby shops and offices in the area. The explosion could be heard from afar.
Qureshi said that it could not be confirmed what the intended target of the militants was.
The blast also damaged three vehicles and three motorcycles parked close to the Nadra office.
“Most of the victims are civilians,” Qureshi said.
The injured were rushed to the Civil Hospital for medical treatment where the doctors said the condition of one of the injured was serious.
According to the bomb disposal squad, more than 10 kilograms of explosives were planted in the motorcycle.
Police and Frontier Corps were quick to arrive at the scene. They cordoned off the area as investigation into the incident went underway.
There was no immediate claim of responsibility for the attack.
In a separate incident, two children were injured when they touched a bomb planted on a road side in Quetta's Ittehad Colony area, police said.
Imran Qureshi, the Superintendent of Police said two children walking on the road hit a road side bomb in Muslim Ittehad Colony area of the Balochistan capital. The injured children were shifted to Civil Hospital Quetta for medical treatment.