The explosion, in Kalya in Orakzai Agency, took place just before 9 a.m. local time (10.30 p.m. ET Wednesday), according to Khalid Iqbal, police deputy commissioner in Orakzai. The majority of the dead were Shia, he added.
The blast took place inside the vegetable section of the market, Iqbal said.
At least 51 people were injured, 17 critically, according to Amin Ullah, the District Administrator for Kalaya. They have been moved to the larger towns of Kohat as well as Peshawar via ambulance, Ullah said.
No group has yet claimed responsibility for the attack.