The attack occurred at Bannu in Khyber-Pakhtunkhwa province, located a short distance from the lawless North Waziristan tribal region, at 6 am, officials said.
The powerful explosion damaged the police station.
Four policemen and five passers-by were injured in the blast, the officials said.
The injured were taken to a nearby hospital.
The blast also blew out the windows of several buildings and damaged nearby property.
A large contingent of police cordoned off the area and conducted a search operation.
No group claimed responsibility for the incident though such attacks are usually blamed on the banned Pakistani Taliban.
