Authorities say nine policemen were among those killed.
The attacker drove his vehicle into the police station Monday in Lakki Marwat in Khyber Pakhtunkhwa province, near tribal areas that are a stronghold of the Taliban. No one has claimed responsibility for the attack.
The police station was destroyed, and and at least one nearby building was damaged in the blast.
Officials say emergency workers are digging through the rubble to rescue people trapped in the debris, and to search for more possible victims.
A suicide bomber last week killed at least 65 people in the southwestern city of Quetta.
That attack came just days after three suicide bombers killed 31 people and wounded hundreds more during a Shiite mourning procession in Lahore. The Pakistani Taliban claimed responsibility.