Iran's new supreme leader Mojtaba Khamenei is injured but "safe and sound", the son of the president said Wednesday, offering the first official explanation for why the 56-year-old has not been seen since his appointment at the weekend.

"I heard news that Mr Mojtaba Khamenei had been injured. I have asked some friends who had connections," Yousef Pezeshkian, who is also a government adviser, wrote in a post on his Telegram channel.