Rescue efforts were initiated and the injured were shifted to Lady Reading Hospital in Peshawar.
Security forces cordoned off the area and a search operation was initiated.
Being the main market of the area, Firdous Market was crowded when the bomb blast took place.
Reuters reported that the incident was a suicide bombing while Express News reported that the bomb was planted in a mini truck.
The target of the attack in the town of Darra Adam Khel appeared to be members of a pro-government militia created to fight Taliban militants, the officials said, adding that the death toll may rise because scores of people were wounded.
10 shops were also destroyed in the blast and many vehicles were damaged.
Earlier, nine people were killed and 21 others sustained injuries in a bomb blast in the Nishtar Road area of Sibi, some 240 kilometres from Quetta.