The Tehrik-e-Taliban Pakistan took responsibility for the blast, which occurred as people were leaving the mosque after Friday prayers in Kalaya, Orakzai Agency, The News International reported.
The explosion also was near the offices of the city's political administration and security forces.
Some sources told the Pakistani newspaper the explosives were detonated in the grocery, while others said the bomb was in a vehicle was parked in the area and was triggered with a remote-controlled device.
'Happy' fan videos make Pharrell cry [VIDEO]
Pregnant Mila Kunis wins 'Best Villain' at MTV Movie Awards