Everyone on board a Ukrainian aircraft carrying 180 passengers and crew that crashed close to Iran's capital, Tehran, has died, Iranian state television has reported.
The plane had taken off from Imam Khomeini International Airport, the report said.
It went down in farmland outside of the city.
Authorities initially blamed a mechanical problem for the crash.
A Government official, Pir Hossein Kulivand, said rescuers were trying to collect the dead.
An investigation team was at the site, civil aviation spokesman Reza Jafarzadeh said.
Flight data from the airport showed a 737-800 flown by Ukraine International Airlines took off on Wednesday morning, then stopped sending data almost immediately afterwards, according to website FlightRadar24.
The airline did not immediately respond to a request for comment.
The crash came hours after Iran launched a ballistic missile attack targeting two bases in Iraq housing US forces in retaliation for the killing of Revolutionary Guard General Qassem Soleimani.
