Iranian state television and a Kurdish exile group are reporting that at least 11 people have been killed in the collision of a tanker carrying tar and a passenger bus in Iran's Kurdistan Province.
State television said the crash occurred on July 10 just before midnight some 400 kilometers west of Tehran in the city of Sanandaj.
The Twitter account of the Paris-based Democratic Party of Iranian Kurdistan posted what it said were videos of the aftermath of the accident.
It quoted sources as saying 20-30 people had died in the accident.
The casualty figures could not immediately be independently confirmed.
Authorities said the tanker's brakes failed before it smashed into the bus near a bus terminal in Sanandaj, igniting both vehicles.
According to UNICEF figures, Iran's rate of traffic accidents is 20 times the world's average, a result of poor roads and lax traffic enforcement.