Former leader Ayatollah Ali Khamenei was killed during a wave of US-Israeli attacks on Saturday.

"The American-Zionist criminals attacked the Assembly of Experts building in Qom," south of Tehran, according to the Tasnim news agency.

The assembly is tasked with appointing, supervising and potentially dismissing the supreme leader.

Local media showed footage of the building severely damaged in the strikes.

There was no information on any potential casualties.

The Mehr news agency reported that the building was no longer being used for meetings.

Tasnim reported that strikes had already targeted the main headquarters of the Assembly of Experts in Tehran on Monday.

Iran declared on Sunday the start of a transition process after confirming Khamenei's death.

The plans include the formation of an interim leadership council including the president, the head of the judiciary and a jurist from the Guardian Council, the body that oversees legislation and vets electoral candidates.

Also playing a central role is Iran's top security chief Ali Larijani.

The interim leadership council will lead the country while a permanent successor is found for the supreme leader.