The Treasury said Faleh Fayyadh, head of the state-sponsored network of pro-Iran fighters, was responsible for brutal attacks on protesters in October 2019.

"By directing and supervising the murder of peaceful Iraqi demonstrators, Iran-aligned militants and politicians such as Faleh Fayyadh have been waging a violent campaign against Iraqi democracy and civil society," said Treasury Secretary Steven Mnuchin.

The PMF -- Hashed al-Shaabi in Arabic -- has close ties to Tehran but is overseen by the Iraqi government, with Fayyadh its chairman and top commander.

Secretary of State Mike Pompeo said in a statement that Fayyadh was also the member of a "crisis cell" supported by the Iranian Islamic Revolutionary Guards, branded a terrorist organization by the United States.

"Iran-aligned (PMF) forces continue to wage a murderous campaign against political activists in Iraq who are calling for free and fair elections, respect for human rights, and transparent and accountable governance," Pompeo said in a statement.

Fayyadh is one of the most senior Iraqi officials to be placed on the US sanctions blacklist.

He recently took part in public commemorations organized by Iraq on the one-year anniversary of the US killing of Islamic Revolutionary Guard commander Qasem Soleimani and Fayyadh's Iraqi lieutenant Abu Mahdi al-Muhandis.

The sanctions seek to freeze any assets a designated person has under US jurisdiction and bans American firms -- including banks and other companies with US branches -- from doing business with them.