Two rockets targeted Baghdad's ultra-secure Green Zone that houses the US embassy early Sunday, Iraq's security forces said in a statement.

"The Green Zone in Baghdad was the target of two Katyusha rockets. The first was shot down in the air by C-RAM defence batteries, the second fell in a square, damaging two vehicles," the statement said.

A security source told AFP that the shot down rocket fell near the US embassy, while the second came down roughly 500 metres (1640 ft) away.

Previously, the source told AFP that two rockets had been shot down near the US embassy.

No one claimed responsibility for the attack.

In recent months, dozens of rocket assaults or drone bomb attacks have targeted US troops and interests in Iraq.

The attacks are rarely claimed but are routinely pinned on pro-Iran factions in Iraq.

The latest rocket salvo comes after the country this week announced the end of the "combat mission" on its territory of the anti-jihadist coalition led by Washington.

But roughly 2,500 American soldiers and 1,000 coalition soldiers deployed in Iraq will remain in the nation to pursue a role of training, advice and assistance.

Pro-Iran factions in Iraq are calling for the departure of all US forces stationed in the country.

The attack also coincides with the 10th anniversary of the departure of US troops from Iraq on December 18, 2011, after the invasion and overthrow of Saddam Hussein in 2003.

Washington then deployed its troops to the country to fight the Islamic State (IS) group, which had captured large swathes of the nation in a lightning offensive.

At the beginning of November, Iraqi Prime Minister Mustafa al-Kadhimi escaped unharmed from an unclaimed drone bomb attack, which targeted his official residence in the Green Zone.

In September, an "armed drone" attack targeted Erbil international airport in Iraqi Kurdistan, where there is a base hosting coalition troops.