One of the tourists in critical condition was transferred to hospital in Shiraz by helicopter, Mizan Online website reported, quoting the head of Iran's emergency services.
Some 10 ambulances and a bus were dispatched to the scene to ferry the others to hospital, it said.
State news agency IRNA said two Iranians, the driver and a tour guide, were among the injured.
The bus driver had lost control due to high speed on a rainy road between Shiraz and Saadat Shahr, a small town about 20 kilometres from the ancient ruins of Persepolis.
Please whitelist us to continue reading.