"The government of Iraq should listen to the legitimate demands made by the Iraqi people who have taken to the streets to have their voices heard," Secretary of State Mike Pompeo said, urging all sides to refrain from violence.

"The government of Iraq's investigation into the violence in early October lacked sufficient credibility and the Iraqi people deserve genuine accountability and justice," he said in a statement.

More than 250 people have died in demonstrations that broke out on October 1 from rage over corruption and unemployment.

The protesters are seeking the ouster of Prime Minister Adel Abdel Mahdi, who maintains warm albeit complicated relations with the United States as well as its arch-rival Iran.

Pompeo's remarks came hours after Iraq's top Shiite cleric Grand Ayatollah Ali al-Sistani, who holds great sway over government decision-making, warned that no foreign actor should be allowed to "impose its will" in Iraq.

Iran's supreme leader Ayatollah Ali Khamenei on Wednesday urged protesters both in Iraq and Lebanon to pursue their demands through "legal frameworks."