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

In a statement, the assembly confirmed Mojtaba Khamenei's election as the country's third supreme leader, citing "the decisive vote of the respected representatives" of the assembly.

"In today's extraordinary session, Ayatollah Seyyed Mojtaba Hosseini Khamenei ... is appointed and introduced as the third leader of the sacred system of the Islamic Republic of Iran," the statement said.

Following the announcement, Iran's Islamic Revolutionary Guard Corps (IRGC) immediately pledged allegiance to the new supreme leader, voicing its readiness to follow his instructions.

Mojtaba Khamenei, born in 1969, is the son of Iran's late Supreme Leader Ali Khamenei, who was killed in the joint US-Israeli strikes.

Mojtaba has been widely speculated as the new supreme leader even before the announcement. Israel and the United States have both issued threats to Iran in this regard.

On Wednesday, Israel threatened that whoever Iran chooses as its new supreme leader would be "a target for elimination."

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

Trump also warned that if Iran selects a new leader who "continues Khamenei's policies," the United States will be forced to return to war "within five years."

The United States and Israel launched surprise airstrikes on Tehran and other Iranian cities on Feb 28, killing Ali Khamenei, along with some of the leader's family members, Iran's senior military commanders and civilians. Iran responded through several waves of missile and drone attacks targeting Israel and US assets across the Middle East.