The bomb, believed to be hidden in a rickshaw, exploded as the police van passed through an area on the outskirts of Dera Ismail Khan city in Khyber Pakhtoonkhwa province, TV news channels quoted police sources and witnesses as saying.
Over 10 others were also injured in the blast. Deputy Superintendent of Police Iqbal Khan, his bodyguard and driver, two children and a woman were killed in the attack that claimed 12 lives.
Khan was driving from his home to work when the blast occurred. Several policemen and passers-by were also injured in the blast.
Witnesses said that the police van and the rickshaw were destroyed in the blast that occurred at Kachi Paind Khan neighbourhood of Dera Ismail Khan. No group has claimed responsibility for the attack but authorities suspect that the Pakistani Taliban orchestrated the blast.
Militants regularly target security forces and police teams in their bloody campaign against the government in Pakistan's north-west.
Image: Security officials survey the site of a suicide bomb attack in Dera Ismail Khan | Photograph: Mustansar Baloch/Reuters