Iranian state TV says at least four cars hit one another in the pile-up near the town of Naeen, about 350 kilometers (220 miles) southeast of Tehran. Eight Iranians and two Afghans were also injured.
The report says three of the cars burst into flames after the crash.
Iran has one of the world's worst traffic safety records, with more than 400,000 accidents and about 20,000 deaths on its roads every year.
The high death tolls are blamed on speeding, unsafe vehicles, widespread disregard of traffic laws and inadequate emergency services.