Tehran, Iran - Mojtaba Khamenei, son of the late Ayatollah Ali Khamenei, has been elected as Iran's new supreme leader, Iranian state news agency IRNA reported on Sunday.

Ali Khamenei was killed in an Israeli airstrike in Tehran on February 28, as part of the first wave of unprovoked attacks launched against Iran by Israel and the US.

The Iranian constitution stipulates that the 88 clerics in the Assembly of Experts determine the new head of state.

The assembly did not hesitate for a moment, "despite the acute war situation and direct threats from enemies," according to a statement published by IRNA. It said the decision was made after "careful and comprehensive deliberations."

The supreme leader of the Islamic Republic has the final say in all political and military matters.

Before the announcement, US President Donald Trump again threatened Iran if he is not involved in deciding who would replace Ali Khamenei.

"He's going to have to get approval from us," he claimed on ABC News. "If he doesn't get approval from us he's not going to last long."

Previously, he had told Axios that Mojtaba Khamenei was an "unacceptable" choice and dismissed him as "a lightweight."

Iranian Foreign Minister Abbas Araghchi has rejected any notion of US interference before the appointment.

"We allow nobody to interfere in our domestic affairs," Araghchi told NBC News. "This is up to the Iranian people to elect their new leader."