The bomb was planted near an electricity tower, which was damaged by the blast.
Two persons passing by were killed by the explosion in Badabher, a suburb of Peshawar, police officials said.
Police launched a search operation after the blast but were unable to make any arrests.
No group claimed responsibility for the incident though such attacks are usually blamed on the Tehrik-e-Taliban Pakistan, which has killed hundreds of people in bombings and suicide attacks in the northwest over the past five years.
