A Ukrainian airliner carrying 176 people crashed on Wednesday due to technical problems soon after taking off from Tehran's Imam Khomeini airport, and all aboard were killed, Iran's state television and Ukraine's leaders said.
The Boeing 737 belonging to Ukraine International Airlines crashed near the airport and burst into flames.
Ukraine President Volodymyr Zelenskiy said there were no survivors.
"My sincere condolences to the relatives and friends of all passengers and crew," Zelenskiy said in a statement, adding that Ukraine was seeking to establish the circumstances of the crash and the death toll.
Iranian state TV and Ukraine's prime minister said 167 passengers and 9 crew were on board.
There was no official word from Ukraine International Airlines.
"The fire is so heavy that we cannot (do) any rescue... we have 22 ambulances, four bus ambulances and a helicopter at the site," Pirhossein Koulivand, head of Iran's emergency services, told Iranian state television.
Television footage showed debris and smouldering engine parts strewn across a field, and rescue workers with face masks retrieving bodies of the victims.
According to air tracking service FlightRadar24, the plane that crashed was Flight PS 752 and was flying to Kiev. The plane was three years old and was a Boeing 737-NG, it said.
A spokesman for Boeing said the company was aware of media reports of a plane crash in Iran and was gathering more information. The plane manufacturer grounded its 737 MAX fleet in March after two crashes that killed 346 people.