The incident occurred in Tank district, which borders South Waziristan tribal region. Officials said an assistant sub-inspector was killed.
The injured were taken to the district headquarters hospital. Police forces rushed to the site and cordoned off the area in a bid to arrest those responsible for the bombing.
In a separate incident, three persons were gunned down and another injured in an attack by unidentified men in a suburb of Peshawar.
The incident occurred in Mashokhel area. The men fired at a house, killing three persons instantly, police said. The attackers fled from the scene.