The bus was carrying Congress supporters to Dediapada town in tribal-dominated Narmada district where party vice president Rahul Gandhi is scheduled to address a public gathering, they said.
The incident took place before noon when the bus with 35 people onboard overturned after losing balance at a sharp turn at Kanja village in Vyara tehsil on Ukai Dam canal road, a Mandvi police station official from neighbouring Surat district said.
The injured have been admitted to Bardoli civil hospital in Surat metropolitan region.