TEHRAN, May 22, 2024 (BSS/AFP) - Large crowds of Iranians are expected to gather in Tehran on Wednesday to pay tribute to late president Ebrahim Raisi, who was killed in a helicopter crash.

Supreme leader Ayatollah Ali Khamenei will lead prayers ahead of funeral processions for Raisi and seven members of his entourage, including foreign minister Hossein Amir-Abdollahian.

The helicopter crashed Sunday on a fog-shrouded mountainside in northern Iran on the way to the city of Tabriz after they attended the inauguration of a dam project on the border with Azerbaijan.

A huge search and rescue operation was launched, involving help from Turkey, Russia and the European Union. State television announced Raisi's death early on Monday.

Raisi, who was widely expected to succeed Khamenei as supreme leader, was 63.

In the capital, huge banners have gone up hailing the late president as "the martyr of service", while others bade "farewell to the servant of the disadvantaged".

Tehran residents received phone messages urging them to "attend the funeral of the martyr of service".

The processions, which will be attended by foreign dignitaries, are planned to set off from the University of Tehran and head to the vast Enghelab Square in the city centre, according to state media.

- Burial in Mashhad -

Funeral rites for the late president and his entourage began on Tuesday with tens of thousands of black-clad mourners in attendance in the city of Tabriz and the Shiite clerical centre of Qom.

From Tehran, the bodies will be moved to South Khorasan province before being transferred to Raisi's home city of Mashhad in the northeast, where he will be buried on Thursday evening after funeral rites at the Imam Reza shrine.

Khamenei, who wields ultimate authority in Iran, has declared five days of national mourning and assigned vice president Mohammad Mokhber, 68, as caretaker president until the June 28 election for Raisi's successor.

Iran's top nuclear negotiator Ali Bagheri, who was Amir-Abdollahian's deputy, has been named acting foreign minister.

The country's armed forces chief of staff Mohammad Bagheri has ordered an investigation into the cause of the helicopter crash.

Raisi was elected president in 2021, succeeding the moderate Hassan Rouhani at a time when the economy was battered by US sanctions imposed over Iran's nuclear activities.

The ultra-conservative's time in office saw mass protests, a deepening economic crisis and unprecedented armed exchanges with arch-enemy Israel.

After his death, global allies Russia and China and regional powers voiced their condolences, as did NATO, while the UN Security Council observed a minute of silence.

Messages of condolence also flooded in from Iran's allies around the region, including Syria, Palestinian militant group Hamas and Lebanese militant group Hezbollah, both of which are backed by Tehran.