What we know so far about the helicopter crash that killed Iran's president

The helicopter crash that killed Iran's president and foreign minister has sent shock waves around the region.

Iranian state media on Monday said that President Ebrahim Raisi, the country's foreign minister, Hossein Amirabdollahian, and others had been found dead after an hours-long search through a foggy, mountainous region of the country's northwest. State TV gave no immediate cause for the crash.

Here's what we know so far.

The helicopter on Sunday was carrying Raisi, Amirabdollahian, the governor of Iran's East Azerbaijan province and other officials, according to the state-run IRNA news agency.

Raisi was returning after travelling to Iran's border with Azerbaijan to inaugurate a dam with Azerbaijan's President Ilham Aliyev when the crash occurred in the Dizmar forest in East Azerbaijan province.

IRNA said the crash killed eight people including three crew members aboard the Bell helicopter, which Iran purchased in the early 2000s.

Iranian officials said the mountainous, forested terrain and heavy fog impeded search-and-rescue operations, which continued overnight.

The president of the Iranian Red Crescent Society, Pir-Hossein Koulivand, said Sunday evening that 40 search teams were on the ground despite "challenging weather conditions." Because of the bad weather, it was "impossible to conduct aerial searches" via drones, Koulivand said, according to IRNA.

It was not until early Monday that officials announced the helicopter had been found and all of its occupants were dead.

Early Monday, Turkish authorities released what they described as drone footage showing what appeared to be a fire in the wilderness that they "suspected to be wreckage of a helicopter." The co-ordinates listed in the footage put the fire about 20 kilometres south of the Azerbaijan-Iran border on the side of a steep mountain.

Footage released by IRNA showed what the agency described as the crash site, across a steep valley in a mountain range. Soldiers speaking in the local Azeri language said: "There it is, we found it." Shortly after that, state TV in an on-screen scrolling text said: "There is no sign of life from people on board."

Raisi was seen as a protege to Iran's Supreme Leader Ayatollah Ali Khamenei and a potential successor for his position within the country's Shia theocracy.

Under the Iranian constitution, if a president dies, the country's first vice-president — in this case, Mohammad Mokhber — would become president. Khamenei has publicly assured Iranians that there would be "no disruption to the operations of the country" as a result of the crash.

Khamenei has named Mokhber as the caretaker president in line with the constitution, which says a new presidential election should be called within 50 days.