Government spokesman Bassem al-Awadi said in a statement that "with deep sorrow, we extend our condolences to the noble people of Iran and the entire Muslim world" after Khamenei was killed in "a blatant act of aggression".

He said the government had announced three days of mourning, while urging an immediate cessation of military operations that "are driving the region to unprecedented levels of violence".

Iran wields a significant influence in Iraqi politics, and also backs armed groups, whose power has grown both politically and financially.

Iraq has for decades been a proxy battleground between the US and Iran.

The Coordination Framework, a ruling coalition of Shiite groups with varying degrees of links to Iran, said "with deep sorrow and profound grief, we mourn the passing of the martyred leader, Ayatollah Ali Khamenei".

His "blood will remain a guiding light for all generations" and "the curse will continue to haunt the murderous Zionists for all time", the coalition added.

Influential cleric Moqtada Sadr meanwhile said in a statement "we extend our condolences to the Islamic world", and declared a three-day period of mourning.