Provincial police chief Abdul Razzq Cheema said on January 7 that an explosive-laden motorbike blew up as a vehicle carrying security forces was passing by.
Two security-force personnel were among those injured.
The attack was claimed by Jamaat ul-Ahrar (JuA), a breakaway faction of the Pakistani Taliban.
Quetta is the capital of the resource-rich Balochistan Province, which borders Afghanistan.
The province has been plagued by sectarian violence, Islamist militant attacks, and a separatist insurgency that has led to thousands of casualties since 2004.