An Iranian military commander warned the United States and Israel on Thursday against any attack on Iran as it prepares for the state funeral of Supreme Leader Ayatollah Ali Khamenei, who was killed in airstrikes on the first day of the war.

"We warn the enemies of Iran, especially the US and the Zionist regime (Israel), to avoid any miscalculation and to think about the harsh retaliation our armed forces would make to any threat and aggression against our country,” Ali Abdollahi, commander of Khatam al-Anbiya Central Headquarters, said in a statement carried by state media.

Funeral processions for Khamenei will begin on July 4 in Tehran and conclude on July 9 with his burial in his hometown of Mashhad, with additional ceremonies planned in Qom and Iraq in-between these dates.

On Wednesday, Iranian Foreign Minister Abbas Araghchi gave a similar warning that Tehran would deliver an immediate and powerful response to any threat against its people or leadership after comments by Israeli Defence Minister Israel Katz that Iran's current Supreme Leader Mojtaba Khamenei was "marked for death."

Iranian media reported heightened security measures during the funeral period, while the head of Iran’s Civil Aviation Organisation said on Wednesday that temporary airspace restrictions would be implemented over several cities including Tehran and Mashhad.