In his first statement since becoming Iran's supreme leader, Ayatollah Mojtaba Khamenei has said that all US bases must be immediately closed in the region or they will be attacked.

The new leader, the son of slain leader Ali Khamenei, has not been seen since the war began. His statement was read aloud by a presenter on IRIB, Iran's state broadcaster.

Khamenei said that Tehran believes in friendship with neighbouring countries, but that it will continue to target US bases.

"Iran, without seeking to establish dominance in the region, is fully prepared for unity and warm relations with its neighbours," he said.

"The countries of the region must close down the US military bases; otherwise, we will be forced to attack them again."