The country’s presidential spokesman said Iran was going through a “difficult” situation.

“We are experiencing difficult and complicated conditions. It is the right of the people and the media to be aware of the latest news about the president’s helicopter accident,” Ali Bahadori Jahromi said. 

“In these moments, patience, prayer and trust in relief groups are the way forward.”

Mr Raisi, a hardliner who formerly led Iran’s judiciary, quickly ascended the ranks of the Islamic Republic, and is now considered a potential successor to the supreme leader.

He won Iran’s closely stage-managed 2021 presidential election, a vote marked by the lowest turnout in the Islamic Republic’s history.

His victory brought all branches of power under the control of hardliners, after eight years in which the presidency had been held by Hassan Rouhani, a pragmatist who entered into a nuclear deal with Washington.

However, Mr Raisi’s standing may have been dented by widespread protests against clerical rule and a failure to turn around Iran’s economy, hamstrung by Western sanctions.

He was sanctioned by the US in part over his involvement in the mass execution of thousands of political prisoners in 1988, when he served as a member of the “death chamber” that decided their fates.

Raisi presided over crackdown on protests

Under Mr Raisi, Iran has continued arming proxy groups in the Middle East, such as Yemen’s Houthi rebels and Hezbollah in Lebanon.

He also presided over the crackdown on several nationwide protest movements, the most recent being those that swept the country after the death of Mahsa Amini, a young woman detained for improperly wearing a headscarf.

More than 500 people were killed and 22,000 detained in the months-long crackdown by the morality police and security services.

Mr Abdollahian, 60, has been Iran’s foreign minister since 2021 and is known for his support of the Iran-backed “Axis of Resistance” against Israel and the US.

According to the constitution, the vice-president would assume power after the death of a president, with elections to follow.

Russia, now one of Iran’s closest allies, offered its help in the search for Mr Raisi. “Russia is ready to extend all necessary help in the search for the missing helicopter and the investigation of the reasons for the incident,” Maria Zakharova, the foreign ministry spokesman, said.

The US State Department said it was closely following the incident, and Joe Biden, the US president, had been briefed on the situation.

Ilham Aliyev, the Azeri president who had been with Mr Raisi on Sunday morning, said: “Today, after bidding a friendly farewell to the President of the Islamic Republic of Iran, Ebrahim Raisi, we were profoundly troubled by the news of a helicopter carrying the top delegation crash-landing in Iran.”