"We can now confirm that 15 people have died in the explosion today". "Among the victims are security personnel and civilians", he said.
In August a year ago, at least 74 people were killed in a suicide attack on the city's Civil Hospital, while another 60 were killed in an attack on a police academy two months later. The terrorists do not want the people to celebrate Independence Day, he added.
"Our resolve (to fight the menace of terrorism) won't succumb to any challenge", the Army Chief was quoted as saying by the Inter Services Public Relations (ISPR) on Saturday.
It added that incendiary explosives were used in the blast that sparked fires in nearby vehicles.
The ISPR confirmed that seven civilians were among the 15 martyrs, while 25, including 15 civilians, were injured in the attack.
Army troops have also reached the incident site and cordoned off the area.
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Some of the injured were shifted to Civil Hospital Quetta and an emergency was declared in hospitals in the vicinity.
Provincial home minister Sarfraz Bugti and government spokesman Anwar ul Haq Kakar confirmed the death toll but put the number of wounded at 32.
Balochistan Home Minister Sarfaraz Bugti refused to give any information about the nature of the blast saying "rescue operations are our priority".
Balochistan has oil and gas resources but is afflicted by Islamist militancy, sectarian violence between Sunni and Shiite Muslims and a separatist insurgency.
Rescue services reached the site promptly after the explosion.
Militant groups operating in the province have previously claimed responsibility for attacking security forces. Fire fighters are trying to control the fire after the explosion. The Balochistan Assembly, Quetta Law College, a private hospital and many offices are located in the area where the explosion occurred.