Two rockets struck Baghdad's heavily fortified Green Zone, home to the U.S. embassy, causing property damage but no casualties, Iraq's military said early Sunday.

One rocket was destroyed by the embassy's C-RAM defense system. Another fell near a national monument, causing damage to two civilian vehicles, the statement said. An investigation was launched by Iraqi security forces.

Along with the U.S. embassy, the Green Zone houses other foreign diplomatic missions and Iraqi government buildings. The zone is a frequent target of rocket and drone attacks that American officials blame on Iran-backed Iraqi militia groups.

Iran-aligned groups have vowed revenge on the U.S. for a 2020 drone strike that killed Iranian general Qassem Soleimani and Iraqi militia commander Abu Mahdi al-Muhandis. They have conditioned the end of attacks against the U.S. presence in Iraq on the exit of American troops from the country.

The U.S.-led coalition formally ended it's combat mission supporting Iraqi forces in the ongoing fight against the Islamic State group this month. Some 2,500 troops will remain as the coalition shifts to an advisory mission to continue supporting Iraqi forces.

The rocket attacks, once near-daily occurrences, have slowed in recent months. In November, an explosive-laden drone targeted the residence of Iraqi Prime Minister Mustafa al-Kadhimi in an assassination attempt.