The incident occurred when the speeding bus, heading for Dahod from Godhra in Panchmahals district, collided with the truck parked on roadside near Orwada village, Panchmahals taluka police inspector M B Machhar said.
"The bus was carrying passengers mostly from Dahod and also from neighbouring Madhya Pradesh, when it hit the stationary truck killing four persons on the spot and injuring 21 others. One more person died in Godhra civil hospital where they were taken," he said.
The deceased included two children, aged around 5 and 12, and two women.
Two of the deceased have been identified as Amit Ganawa (5) and Manjuben Mansinhbhai, while the names of others were yet to be ascertained, Machhar added.