The militants exchanged fire with security forces and at least one policeman was killed, TV news channels reported.
At least five militants were inside the police station, media reports said.
There was no word from authorities on the incident.
Security forces cordoned off the area and surrounded the police station.
Army soldiers were called in to reinforce the local police.
It could not immediately be ascertained if the militants had taken any hostages. No group claimed responsibility for the incident.
In April, nearly 400 prisoners escaped from the central prison in Bannu after an attack by scores of fighters of the banned Tehrik-e-Taliban Pakistan.
The attack was carried out to free Adnan Rashid, who was sentenced to death by a military court for an attempt on the life of former President Pervez Musharraf in 2003.