Istanbul, Turkey — President Trump said Iran will be held responsible after a mob forced its way onto the U.S. Embassy compound in Baghdad. It was retaliation for U.S. airstrikes that killed members of a militia backed by Iran.

Thousands of protestors were somehow able to get past Iraqi security forces, into the fortified Green Zone and reach the U.S. Embassy compound. They vented their anger with fires and with rocks, they pulled down signs, smashed a security booth and broke into an embassy reception area. The embassy is a place of plotting against Iraq, said militia leader Qais Al-Khazali.

American guards reportedly fired tear gas and U.S. officials said the military is sending reinforcements to the embassy from units already in Iraq. But U.S. personnel are safe, and there are no evacuation plans.

Protesters and militia fighters gather to condemn U.S. airstrikes on bases belonging to Iran-backed paramilitary forces, outside the main gate of the U.S. Embassy in Baghdad, Iraq, December 31, 2019. THAIER AL-SUDANI/REUTERS

The violence was a response to U.S. airstrikes on Sunday, targeting a militia group in Iraq that's backed by Iran. The U.S. strikes killed at least 25 militia fighters and were an act of retaliation for the killing of a U.S. citizen, an American contractor, working at an Iraqi military base, who died in a rocket attack last week.

The U.S. airstrikes have fueled anti-American fervor, which is never far from the surface and the protests show the political power wielded by militia groups backed by Iran. With Iran and the U.S. vying for influence in Iraq, and tensions high, the fear is a full-blown proxy war fought in a country already steeped in blood.

President Trump tweeted that Iran will be held responsible for the violent protests and will pay a "big price." But nearly 17 years after invading Iraq, the U.S. Embassy come under attack under the noses of Iraqi security forces and the U.S. is competing with Iran to influence the country's government.