Iranians gathered on Tuesday to mourn at the funerary procession of president Ebrahim Raisi in the northwestern city of Tabriz, the capital of East Azerbaijan province where he died unexpectedly in a helicopter crash.

The helicopter lost communication while it was on its way back to Tabriz after Raisi attended a joint inauguration of a dam with his Azeri counterpart, Ilham Aliyev, on their common border.

A massive search and rescue operation started Sunday afternoon when two other helicopters in Raisi's convoy lost contact with his aircraft amid harsh weather conditions in the mountainous region.

State TV early Monday broke the news of his death, saying "the servant of the Iranian nation, Ayatollah Ebrahim Raisi, has achieved the highest level of martyrdom", showing pictures of him as a voice recited the Koran.

Killed alongside the Iranian president were Foreign Minister Hossein Amir-Abdollahian, members of the provincial authorities of East Azerbaijan and his security team.

Iran's military chief of staff Mohammad Bagheri on Monday ordered a probe into the cause of the crash.

Following the confirmation of Raisi's death, international condolences poured in while people in cities across the Islamic republic gathered to mourn the late president and his companions.

Thousands of mourners holding portraits of Raisi gathered Monday at central Valiasr Square in the capital Tehran.

National mourning

Supreme leader Ayatollah Ali Khamenei, who has ultimate authority in Iran, declared five days of national mourning and assigned vice president Mohammad Mokhber, 68, to assume interim duties ahead of elections.

State media later announced the presidential election would be held on June 28.

Iran's top nuclear negotiator Ali Bagheri, who served as deputy to Amir-Abdollahian, was tapped to serve as the acting foreign minister.

After leaving Tabriz, Raisi's body will arrive in Iran's Shiite clerical centre of Qom Tuesday before being moved to Tehran.

Khamenei is due to hold prayers at a farewell ceremony in Tehran on Tuesday night, ahead of major processions due to begin on Wednesday morning.

Raisi will then be taken to Southern Khorasan province on Thursday morning and later to his hometown of Mashhad, where he will be buried on Thursday evening after funerary rites.

The ultraconservative Raisi, 63, had been in office since 2021, a time during which Iran was rocked by mass protests, an economic crisis deepened by US sanctions, and armed exchanges with arch-enemy Israel.

Raisi succeeded the moderate Hassan Rouhani, at a time when the economy was battered by US sanctions over Iran's contested nuclear programme.

Condolences flooded in from Palestinian militant group Hamas, Lebanon's Hezbollah, and Syria, all members of the so-called "axis of resistance" against Israel and its allies, at a time of high Middle East tensions over the Gaza war.

The war in the Palestinian territory sent tensions soaring and a series of escalations led to Tehran launching hundreds of missiles and drones at Israel in April.

It came in response to an earlier air strike widely blamed on Israel that levelled Tehran's Damascus consulate and killed two Revolutionary Guards generals.

In a speech hours before his death, Raisi emphasised Iran's support for the Palestinians, a centrepiece of its foreign policy since the 1979 Islamic revolution.

Palestinian flags were raised along with the Iranian flags in ceremonies for Raisi across the Islamic republic on Monday.