Ali, a masked protester, told AFP "the martyrdom of Sayyed Ali Khamenei has hurt us".

"We are here because we want the withdrawal of the occupying American forces from Iraq," referring to US-led coalition troops who have recently reduced their presence and are now mostly stationed in northern Iraq.

AFP journalists near the Green Zone reported a heavy security deployment and the closure of the zone's entrance, but protesters kept trying to break in.

Protesters, who had gathered since early Sunday, hurled stones at security forces, who responded with tear gas.

A security source told AFP earlier that "their attempts have been thwarted so far, but they keep trying".

An AFP journalist said protesters, some holding flags of pro-Iran armed groups, cursed the security forces and chanted "for you Khamenei".

Hussein, a protester in his twenties, said "we are here to respond to Khamenei's martyrdom, and I want us to fight the US and Israel".

Khamenei was killed on Saturday as the United States and Israel launched a wave of strikes on the Islamic republic.

Like the US, Iran wields significant influence in Iraqi politics, while also backing armed groups whose power has grown both politically and financially.

Several Iran-backed Iraqi armed groups said Saturday they would not remain "neutral" and would defend the Islamic republic.

The powerful group Kataeb Hezbollah said it would attack US bases after two of its fighters were killed in air strikes in southern Iraq.

Early Sunday, loud explosions were heard near Erbil airport in Iraq's autonomous Kurdistan region, which hosts US-led coalition troops, an AFP journalist said.

He also reported seeing thick black smoke rising from the airport area.

Shortly after, a small pro-Iran group claimed drone attacks on US troops in Erbil.

On Saturday, US-led coalition forces downed several missiles and explosive-laden drones over Erbil, local authorities said.