PHOTOS: Iraqi Shiites break into U.S. Embassy in Baghdad

Dozens of Iraqi Shiite militiamen and their supporters broke into the U.S. Embassy compound in Baghdad on Tuesday, smashing a main door and setting fire to a reception area, prompting tear gas and sounds of gunfire, angered over deadly U.S. airstrikes targeting the Iran-backed militia.

An Associated Press reporter at the scene saw flames rising from inside the compound and at least three U.S. soldiers on the roof of the main embassy building. There was a fire at the reception area near the parking lot of the compound, but it was unclear what had caused it. A man on a loudspeaker urged the mob not to enter the compound, saying: “The message was delivered.”

There were no reports of casualties, but the unprecedented breach was one of the worst attacks on the embassy in recent memory. It followed deadly U.S. airstrikes on Sunday that killed 25 fighters of the Iran-backed militia in Iraq, the Kataeb Hezbollah. The U.S. military said the airstrikes were in retaliation for last week’s killing of an American contractor in a rocket attack on an Iraqi military base that it had blamed on the militia.

The developments represent a major downturn in Iraq-U.S. relations that could further undermine U.S. influence in the region and also weaken Washington’s hand in its maximum pressure campaign against Iran.

Iraq has long struggled to balance its ties with the U.S. and Iran, both allies of the Iraqi government. But the government’s angry reaction to the U.S. airstrikes and its apparent decision not to prevent the protesters from reaching the embassy signaled a sharp deterioration of U.S.-Iraq relations.

Iraqi security forces made no effort to stop the protesters as they marched to the heavily-fortified Green Zone after a funeral held for those killed in the U.S. airstrikes, letting them pass through a security checkpoint leading to the area.

Dozens of protesters pushed into the embassy compound after smashing the gate used by cars to enter the grounds. The protesters, many in militia uniform, stopped in a corridor after about 16 feet and were only about 600 feet away from the main building. Half a dozen U.S. soldiers were seen on the roof of the main building with their guns pointed at the protesters.

Smoke from the tear gas rose in the area, and at least three of the protesters appeared to have difficulties breathing. It wasn’t immediately known whether the embassy staff had remained inside the main building or were evacuated at some point. There was no immediate comment from the U.S. Embassy.

The protesters hanged a poster on the wall that read, “America is an aggressor,” and some commanders of militia factions loyal to Iran joined the protesters. Among those was Hadi al-Amiri, the head of the state-sanctioned paramilitary Popular Mobilization Forces, the umbrella group for the Iran-backed militias.