Security personnel at the US Embassy in Baghdad lobbed tear gas canisters and shot rubber bullets at hundreds of protesters on Wednesday.
Quoting an eyewitness, CNN reports that demonstrators were seen trying to climb the embassy's exterior walls as the protest entered a second day.
Others said the agitating mob was hurling rocks at the building and trying to set fire to its walls and to the security booths at the main entrance.
It marks the second day of mass demonstrations outside the building in Baghdad's heavily fortified Green Zone, in response to US airstrikes on an Iranian-backed militia group on Sunday.
The US carried out airstrikes on five facilities in Iraq and Syria that it says are tied to the Iranian-backed group Kataib Hezbollah, killing dozens of people.
US officials hold Kataib Hezbollah responsible for a growing number of rocket attacks against American facilities in Iraq.
The death of a US contractor in one such attack last week was the last straw for the Trump administration.
US President Donald Trump blamed Iran for both the US contractor's death and Tuesday's attack on the US Embassy in Baghdad, and warned Iran's leaders they would be held responsible for any deaths or destruction at the embassy.
"Iran will be held fully responsible for lives lost, or damage incurred, at any of our facilities," Trump tweeted. "They will pay a very BIG PRICE! This is not a Warning, it is a Threat."
But Iran's Supreme Leader Ayatollah Ali Khamenei responded by tweeting that the US "can't do anything."
"If you were logical - which you're not - you'd see that your crimes in Iraq, Afghanistan... have made nations hate you," Khamenei added.
Paramilitary groups who have been protesting at the embassy on Wednesday asked their supporters to "withdraw" from the area and respect the Iraqi government, according to a statement released by the Popular Mobilization Units (PMU).
It was not immediately clear if supporters were heeding the call by the PMU, and local media reports suggested some factions within the group had rejected the request.
Quoting the eyewitnesses, CNN report says that local law enforcement forces around the embassy had not been seen doing anything significant to stop the protestors demonstrating in front of the compound, or from throwing stones at it.
The airstrikes and ensuing protests come at a time of high tension between the US and Iran, and have stoked fears of a new proxy war in the Middle East.