CAIRO - Mojtaba Khamenei, son of Iran's late Supreme Leader Ali Khamenei, was selected as Iran's new supreme leader, Iran's Assembly of Experts announced Sunday.

Having lost several relatives in US and Israeli attacks and long lived under US sanctions, the new leader has consistently maintained a hardline stance against the West. Experts say he could adopt an even tougher posture toward the United States and Israel than his father did.

Here's a quick overview of Mojtaba Khamenei's background and global reactions to his election as the supreme leader.

Who is Mojtaba Khamenei?

- Mojtaba Khamenei was born in the Iranian holy city of Mashhad in 1969. After Iran's Islamic Revolution in 1979, his family moved to the Iranian capital Tehran.

- After graduating from high school, he joined the Islamic Revolution Guard Corps (IRGC) and served during the final stages of the Iran-Iraq War. He later pursued religious studies in the central Iranian city of Qom and then became a political aide to his father.

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- Mojtaba Khamenei has long assisted his father in handling important state affairs, has a "deep understanding" of major administrative matters, and maintains working relationships with numerous senior officials across successive governments as well as senior military commanders, according to Iranian media reports.

- In 2019, during Donald Trump's first term as the US president, the US government placed Mojtaba Khamenei on its sanctions list, citing his role in carrying out some of the responsibilities of Iran's supreme leader.

- For years, he has been widely regarded as a leading contender to succeed his father, though he has kept a low public profile.

Why Mojtaba Khamenei?

- A member of Iran's Assembly of Experts said that Mojtaba Khamenei's selection as the country's new supreme leader was approved "by the majority of the Assembly of Experts".

- Mojtaba Khamenei has spent years building influence within Iran's political and security apparatus. Palestinian political analyst Abdul Qader Hammad of Al-Aqsa University in Gaza noted his close ties to the IRGC, which bolster his credibility and make it possible to secure support from hardline factions.

- Familiarity with Iran's political system also works in Mojtaba Khamenei's favor. Hammad said that, having served as a key aide to the supreme leader for many years, Mojtaba Khamenei understands the processes behind major policy decisions, which could help facilitate a smooth transition of power.

- In times of crisis, Iranian authorities have historically favored leaders who are trusted and capable of maintaining political continuity. As the son of long-serving Supreme Leader Ali Khamenei, Mojtaba Khamenei is widely seen as someone who could preserve the current trajectory of the country during uncertain times.

Global reactions to his appointment

- Following the announcement, Iran's IRGC immediately pledged allegiance to the new supreme leader, voicing its readiness to follow his instructions.

- Iranians on Monday attended large gatherings across the country to pledge allegiance to the Mojtaba Khamenei.

- Yemen's Houthi group, which is backed by Iran, on Monday welcomed the decision, describing the move as a sign of unity and strength within the Islamic Republic.

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- Iraqi Prime Minister Mohammed Shia' al-Sudani on Monday extended his best wishes to the newly elected supreme leader, voicing Iraq's solidarity with Iran.

- Oman's Sultan Haitham bin Tariq Al Said on Monday congratulated Mojtaba Khamenei on his appointment as Iran's new supreme leader.

- Russian President Vladimir Putin sent a congratulatory message to Mojtaba Khamenei on Monday, stating that Russia has been and will remain a reliable partner of Iran.

- A Chinese Foreign Ministry spokesperson said on Monday the election of Mojtaba Khamenei as Iran's third supreme leader was a decision based on the country's constitution.

- US President Trump has told US news website Axios that it is "unacceptable" for Mojtaba Khamenei to become Iran's new leader, noting that he himself must be personally involved in selecting Iran's next leader.