Police said accident took place at Lekhapani area near Ledo when the van, which was on its way to Margherita from Jagun, collided with a mini-truck coming from the opposite direction.
The van caught fire after the collision and three of its passengers died on the spot, while another lost his life later in hospital.
Three of the dead have been identified as Biju Barman, Ranjita Sinha and Umesh Das. The injured were rushed to nearby hospitals.