The accident occurred on the border between Umbria and Lazio when a bus collided head-on with a camper van on Sunday afternoon.
Four of the dead were on the bus, two of them drivers. The other two victims were in the camper, Rai reports. Another 26 people were injured.
According to preliminary police information, the camper crossed into the opposite lane.
Several other cars were unable to avoid the crash and were also involved. One of the vehicles overturned.
