President Raisi had been in Azerbaijan for the inauguration of a dam and was returning in a convoy of aircraft.
A helicopter carrying Iran’s president has crashed during bad weather, Iranian state media has said.
President Ebrahim Raisi was travelling across the far northwest of Iran following a visit to Azerbaijan.
Rescue teams and the army are trying to reach the scene but are being hampered by heavy fog in a mountainous area.
Contact has been made with a passenger and a crew member of the president’s helicopter, an official told state TV. The unnamed official said contact has been made on several occasions.
Iran latest: Rescuers search for President Ebrahim Raisi after crash
The president was said to be travelling with foreign minister Hossein Amirabdollahian, the governor of East Azerbaijan province and other officials.
Earlier on Sunday, an Iranian official told Reuters news agency that the lives of the president and foreign minister are “at risk”.
“We are still hopeful but information coming from the crash site is very concerning,” said the official, speaking anonymously.
Interior minister Ahmed Vahidi said Mr Raisi was in a convoy of three aircraft but didn’t explicitly confirm he was on the helicopter involved.
Mr Raisi had been in Azerbaijan for the inauguration of a dam with the country’s president, Ilham Aliyev.
“The esteemed president and company were on their way back aboard some helicopters and one of the helicopters was forced to make a hard landing due to the bad weather and fog,” Mr Vahidi said on state TV.
“Various rescue teams are on their way to the region but because of the poor weather and fogginess it might take time for them to reach the helicopter.”
Mr Vahidi added: “The region is a bit [rugged] and it’s difficult to make contact. We are waiting for rescue teams to reach the landing site and give us more information.”
A rescue helicopter tried to reach the site but couldn’t land due to the fog, emergency services spokesman Babak Yektaparast told IRNA.
The army’s chief of staff ordered all resources to be deployed and Iraq has also offered to help.