At least seven people, including four policemen and two women, were injured in a blast near a police vehicle in Dera Ismail Khan on Wednesday.
According to police officials, the van was on routine patrolling when it was targeted.
The bomb which had been planted on the Bannu road within the jurisdiction of the Cantt Police Station went off with a loud bang, police said.
All the injured were shifted to a nearby hospital. Police reached the site and collected evidence after cordoning off the area.
The number of attacks in the country has fallen around 70 per cent, due to a combination of the military offensive against militant bases along the Afghan border and government initiatives to tackle militancy, but attacks on security and civilian targets continue to occur occasionally.