Mojtaba Khamenei was barely known to Iranians when he was named shortly after the killing of his father and longstanding supreme leader, Ali Khamenei, who had been in the post-for-life since 1989, in a US-Israeli airstrike at the start of the Middle East war.

Unseen in public since being named and said to have been wounded in a US-Israeli strike, Mojtaba Khamenei has issued a dozen written messages as leader that have reprised the confrontational ideology of his father.

In a statement read out on Thursday taking aim at Israel and the United States, Mojtaba Khamenei said "the malicious enemy" was seeking to "plant the seeds of doubt, despair, fear, mistrust and division".

Unlike his father, a prominent opponent of the shah who was president in the first decade of the Islamic republic from 1981-1989 before becoming leader, Mojtaba Khamenei has until now held no government position.

But he was believed by observers to be the second-in-command at the office of the supreme leader under the longstanding chief gatekeeper Mohammad Golpayegani.

He is also seen as close to the leadership of the powerful Revolutionary Guards, a connection that may have proved crucial in his selection by the Assembly of Experts clerical body.

- Sanctioned by US -

One of the few official insights into the importance of Mojtaba Khamenei came in November 2019 when the US Treasury announced sanctions against him and other senior Iranian officials, including Golpayegani, on the grounds they were pushing Iran's "radical" agenda around the world.

It said he was designated for representing Ali Khamenei "in an official capacity despite never being elected or appointed to a government position aside from work in the office of his father".

It added: "The Supreme Leader has delegated a part of his leadership responsibilities to Mojtaba Khamenei."

It said Mojtaba Khamenei had "worked closely" with the commanders of the Quds Force -- the branch of the Revolutionary Guards ideological army responsible for operations outside Iran -- and the Basij militia "to advance his father's destabilising regional ambitions and oppressive domestic objectives".

A sign of his potential behind-the-scenes sway came in 2005 presidential elections, when former parliament speaker Mehdi Karroubi wrote a letter to the supreme leader complaining that Mojtaba Khamenei had been intervening on behalf of his ultra-conservative rival Mahmoud Ahmadinejad.

Ahmadinejad went on to cause a sensation by defeating former president Hashemi Rafsanjani. Mojtaba was again seen by some commentators as coordinating the crackdown on protests that followed Ahmadinejad's disputed 2009 election victory.

Leaked US diplomatic cables published by Wikileaks said in 2011 that Mojtaba was "seen by many second only to Golpayegani within the office of the supreme leader".

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

It reported he has earned money from oil sales channelled into investments in luxury British real estate, hotels in Europe and property in Dubai through shell companies in tax havens.

Born in his father's home city of Mashhad in northeastern Iran, Mojtaba Khamenei studied theology in the clerical hub of Qom where he also taught.

He had attained the rank of hojatoleslam -- a mid-ranking cleric -- but was presented as the higher rank of ayatollah upon his appointment as supreme leader.

Mojtaba Khamenei's wife, Zahra Haddad Adel, the daughter of former parliament speaker Gholam Ali Haddad Adel, died in the US-Israeli strikes that killed ex-supreme leader Khamenei, according to the Iranian authorities.