Huge crowds have taken to the streets of Iraq's capital, Baghdad, to demand that US forces leave Iraq.
Powerful Iraqi Shia cleric Moqtada al-Sadr earlier called for a million people to join Friday's march, close to the US embassy in the capital.
Iranian-backed militias are among those protesting in the city.
The US killing of the top Iranian military commander, Gen Qasem Soleimani, on 3 January at Baghdad airport has fuelled tensions.
Also assassinated in the US drone strike was Abu Mahdi al-Muhandis, an Iraqi who had commanded the Iranian-backed Kataib Hezbollah militia group.
Iran responded to Gen Soleimani's assassination by carrying out a ballistic missile attack on two airbases housing US forces in Iraq.
The US later said there were no US casualties in the 8 January attack.
But just hours after the strike, Iran's armed forces fired two missiles at a Ukrainian passenger plane over Iran's capital, Tehran, by mistake, killing all 176 people on board.
What's the latest from Baghdad?
Protesters started to gather in central Baghdad early on Friday, and several hours later, the area was packed with people.
Many carried Iraq's national flags as well as placards denouncing the US military presence in Iraq.
The demonstration threatens to eclipse a separate protest movement involving mainly young people who for several months have been demanding a complete overhaul of the Iraqi government, says the BBC's Martin Patience in Baghdad.
Some 5,000 US soldiers are in Iraq as part of the international coalition against the Islamic State (IS) group.
The two airbases targeted by Iran are in Irbil and al-Asad, west of Baghdad.
How did we get here?
The assassination of Gen Soleimani – head of the Revolutionary Guards' elite Quds Force and architect of Iran's policy in the Read More – Source