After being hit with tear gas, demonstrators who rallied against deadly US air raids heed calls to retreat.

Protesters withdrew from the United States embassy perimeter in Baghdad after the Hashd al-Shaabi (Popular Mobilization Forces) paramilitary force ordered them to leave, a day after their dramatic demonstration.

Iraq's military confirmed on Wednesday that the protesters had left.

On Tuesday, thousands of Iraqi supporters of the largely Iranian-trained group had encircled and vandalised the embassy compound, outraged by US air raids in Iraq and Syria that killed 25 Hashd fighters over the weekend.

Angered crowds marched unimpeded through the checkpoints of the usually high-security Green Zone to the embassy gates, where they broke through a reception area, chanting "Death to America" and spraying pro-Iran graffiti on the walls.

Iraq's caretaker Prime Minister Adel Abdul Mahdi called on the protesters to leave the embassy, but most spent the night in dozens of tents set up outside the perimeter wall.

On Wednesday morning, crowds of men brandished the Hashd's colours, torched US flags and hurled rocks towards the compound.

Security personnel inside responded with tear gas, wounding at least 20 people, the Hashd said.

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