The governor´s office of Afyonkarahisar province said the bus was traveling from the southeastern Diyarbakir province to the Aegean city of Bodrum.
Health Minister Fahrettin Koca tweeted that 42 people were injured, with three in critical condition.
Videos from the scene showed ambulances lined up and a crane holding the bus up.
An injured passenger with a broken arm told official Anadolu news agency that he was half asleep when the bus “flew.” He said people were stuck underneath the bus.
The bus was operated by a company called Star Has Diyarbakir.