According to police, the blast occurred in Sardheri Bazar area in Khyber Pakhtunkhwa's Charsadda district, killing seven persons.
Deputy Inspector General of Police Mardan Range Saeed Wazir said that the bomb, weighing four to five kilogrammes, was planted on a cycle.
Nine others, including two policemen, were also injured in the explosion. The injured have been shifted to the district hospital for treatment.
Today's attack came a day after the immunisation drive in Karachi was suspended following an attack on a vaccination team in the city's Qayyumabad area.
The attack left the windows of the vehicle shattered, injuring the driver of the vehicle and a Lady Health Worker.
Pakistan is one of only three countries in the world where polio remains endemic, along with Afghanistan and Nigeria.