More than 500 people were killed during the months-long movement that began last year, many of them protesters shot by Iraqi security forces who used live ammunition and tear gas to disperse crowds.

Pompeo said the United States was committed to helping Iraq regain and maintain security, despite President Donald Trump's oft-stated desire to reduce and then eliminate the American troop presence there.

Iranian investigators are blaming a misaligned missile battery and miscommunication between soldiers and their commanders for the Revolutionary Guard shooting down a Ukrainian jetliner in January, killing 176 people.

Officials did not say what group they believe launched the rocket attack, but Kataib Hezbollah or another Iranian-backed Shia militia group is likely.

The attack came just before 3:30 a.m. local time, according to Col. Myles B. Caggins III, a spokesman for the U.S. military operation in Iraq. He only said the rockets hit the base hosting U.S. and other coalition forces.

The violence is the latest since protests in Iraq reignited last week after a brief lull amid soaring tensions between Washington and Tehran following a U.S. drone strike that killed top Iranian general Qassem Soleimani in Baghdad earlier this month.

Relations with Iraq were fractured after the U.S. launched a drone strike near Baghdad's international airport on Jan. 3 that killed Iranian Gen. Qassem Soleimani.

The attack by at least six rockets came just days after Iran fired ballistic missiles at two bases in Iraq that house U.S. forces, causing no casualties.

There was no immediate claim of responsibility.

The rocket fell inside the Green Zone's Celebrations Square, near the U.S. embassy.