Israel's military has threatened to target any successor to former supreme leader Ali Khamenei, who was killed over a week ago in a first wave of US and Israeli strikes on Iran.

China's foreign ministry spokesman Guo Jiakun told reporters on Monday that Iran's decision to appoint the younger Khamenei was "based on its constitution".

"China opposes interference in other countries' internal affairs under any pretext, and Iran's sovereignty, security, and territorial integrity should be respected," he said when asked about the threats against the new leader.

Israel and the United States have continued in recent days to pound Iran, which has retaliated by launching waves of missile and drone attacks on Israel and Gulf neighbours hosting US forces.