The passenger car was on its way to Dir district from the mountainous Chitral district in Khyber Pakhtunkhwa when it collided with another car near Ayun area and fell into a river, police said.
Six people, including a woman and a child, were killed in the accident, they said.
The rescue team has retrieved the bodies from the river, they said, adding that the incident had occurred due to speeding.
Road accidents are common in Pakistan. Most of them are caused by careless driving, bad roads and faulty vehicles.
In December, at least 10 people, including six children, were killed when two buses and a pick-up van collided on a highway in the Sindh province.