Fifteen persons travelling in the bus were also injured, he added.
The incident took place in the morning today near Meen Phate on Jaora-Nagda road.
Additional Superintendent of Police (ASP) Jagdish Dabar said the mishap happened when a private bus was trying to overtake a truck and both vehicles collided with another truck coming from the opposite direction.
The impact of the collision was such that one of the trucks overturned and the driver's cabin of the bus and a truck caught fire, he added.
The ASP said that four of the six deceased have been identified and efforts were on ascertain the details of the other two.
The bus was coming from Mandsaur and was headed to Indore, Dabar said.
He said that 15 others travelling in the bus were injured and had been admitted to hospitals in Ratlam, Khachrod and Nagda towns.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)