The accident, the cause of which remains unclear, occurred near Kavar, a town about 1,000 kilometers (600 miles) from the capital, Tehran.
“Unfortunately, 21 deaths have been recorded,” Kavar Hospital director Mohsen Afrasiabi told state television, adding that 29 people were injured.
Also Read: At least 30 injured as vehicle ploughs into crowd outside LA club
Masoud Abed, head of the province’s emergency organisation, said rescue operations are ongoing and final casualty figures will be released after investigations are completed.
Iranian media showed images of a coach lying on its side on a mountain road.
Iran records nearly 17,000 road accident casualties annually, a toll attributed to lax enforcement of safety regulations, the widespread use of aging vehicles, and strained emergency services.