The BBC quoting Iranian state TV said forty-eight people were killed when a small passenger plane crashed in the west of the Iranian capital Tehran.
The aircraft, which was heading to the eastern city of Tabas, went down in a residential area near Mehrabad airport on Sunday morning, state media said.
Passengers included five children, Iran's aviation authority said.
Iran has suffered a series of plane crashes, blamed on its ageing aircraft and poor maintenance record.
Iran is still flying planes bought before the Islamic Revolution in 1979.
International trade sanctions were imposed after the hostage crisis which followed, during which 52 Americans were held hostage in Tehran for 444 days.
Many Iranian planes are fitted with unofficial spare parts.
There have been more than 200 accidents involving Iranian planes in the past 25 years, leading to more than 2,000 deaths.
Initial reports indicate the latest incident involved an Iran-140 jet carrying 48 people, including 40 passengers and eight crew.
The plane was said to have crashed at 9:18 local time (4:48 GMT), shortly after takeoff.