"The gunmen first opened fire on the tankers and after fleeing they attacked a nearby police post in which three police constables and one sub inspector were killed," local police official Sajid Mehmood said.
"Six other police officials were wounded," he added.
The police post was gutted in the attack with the fire brigade trying to put out the blaze that had engulfed the ten Nato vehicles, he said.
According to the eyewitnesses, militants also opened fire at Nato vehicles in Dhok Pathan area, resultantly four tankers caught fire.
Security forces cordoned off the areas after both incidents and launched relief activities.
