Khamenei's successor is set to be named by the top clerical body the Assembly of Experts, with one of its members, Ahmad Khatami, telling Iranian state media on Wednesday that they hoped to vote "at the earliest opportunity".

Contenders for the top position include Alireza Arafi, one of the three members of the interim council running the country, hardliner Mohsen Araki, and even Hassan Khomeini, the grandson of the founder of the Islamic republic in 1979.

Mojtaba Khamenei, 56, would represent a hereditary transition that his father rejected as an idea in 2024.

The Islamic republic put an end to a multi-century royal dynasty headed by the shah.

Born on September 8, 1969, in the holy city of Mashhad in eastern Iran, Mojtaba Khamenei is one of the late supreme leader's six children.

Ayatollah Ali Khamenei died aged 86 on Saturday in Tehran in one of the opening US-Israeli missile strikes of the war.

Because of his discretion at official ceremonies and in the media, Mojtaba's true influence has been the subject of intense speculation for years among the Iranian population as well as in diplomatic circles.

He is the only child of the former supreme leader to hold a public position despite having no official post.

The cleric, who has a salt-and-pepper beard and the black turban of the "seyyed", descendants of the Prophet Mohammed, has been presented by some as the real boss, acting behind the scenes at the heart of power in Iran.

He is regarded as close to conservatives, notably because of his ties with the Revolutionary Guards, the ideological army of the Islamic republic.

This relationship dates back to his service in a combat unit at the end of the war between Iraq and Iran from 1980-1988.

- Security force links -

The US Treasury Department imposed sanctions on Mojtaba Khamenei in 2019 during President Donald Trump's first term, stating that the Iranian represented the supreme leader "despite never being elected or appointed to a government position aside from work in the office of his father".

Ali Khamenei had "delegated a part of his leadership responsibilities" to his son "who worked closely" with Iranian security forces "to advance his father's destabilising regional ambitions and oppressive domestic objectives", it said.

Opponents have notably accused him of playing a role in the violent crackdown that followed the re-election of ultra-conservative president Mahmoud Ahmadinejad in 2009, which triggered a vast protest movement.

According to an investigation by the Bloomberg news organisation, which cited anonymous sources and Western intelligence agency reports, Mojtaba Khamenei has amassed wealth estimated at more than $100 million.

Money from oil sales had been channelled into investments in luxury British real estate, hotels in Europe and property in Dubai through shell companies in tax havens, according to the article.

On the religious front, he studied theology in the holy city of Qom, south of Tehran, where he also taught.

He attained the rank of Hujjat al-Islam, a title given to mid-ranking clerics, below that of Ayatollah held by his father and revolutionary founder Ruhollah Khomeini.

His wife, Zahra Haddad-Adel, daughter of a former speaker of parliament, also died in the US-Israeli strikes that killed the supreme leader, according to Iranian authorities.

Israeli Defence Minister Israel Katz warned on Wednesday that any successor to Ali Khamenei would become "a target".

The Assembly of Experts has 88 members who are elected every eight years.

It has only overseen one leadership transition process to date, when Khamenei was selected in 1989 following the death of Khomeini.