The explosion struck the van at Bayzid Khel bus stop on Kohat Road near Peshawar.
A police official from Peshawar said that the exact nature of the bombing is not known.
Amjad Khan, a paramedic, said that "seven people have died and about five injured" in the attack.
Private media footage showed the vehicle which was destroyed in the bombing.
Nobody claimed responsibility but Pakistani Taliban militants often carry out such attacks.
Around 50,000 people have been killed in over a decade of insurgency in the country.