Iraqi security forces raided Baghdad's main protest site on Saturday and tried to eject protesters in southern cities, firing tear gas and bullets killing four people and wounding dozens more, police and medical sources said.

Shia militia leader Hadi al-Amiri, one of the most powerful figures in Iraq, withdrew his candidacy for prime minister on Tuesday.

Shia cleric Moqtada al-Sadr urged Iraqis on Monday to unite rather than squabble over a possible rerun of the election his bloc won last month, a message apparently tailored to defuse political tension after a ballot box storage depot caught fire.

Moqtada al-Sadr himself cannot become prime minister as he did not run in the election, though his bloc's victory puts him in a position to have a strong say in negotiations.

Iraqis voted on Saturday in the first election since the defeat of Islamic State militants inside the country. Final results are expected on Monday.

Tension between Iraq's Shia leaders mounted on Sunday as the toll from protests in central Baghdad on Saturday increased to six killed, five demonstrators loyal to the fiery cleric Moqtada al-Sadr and one policeman.

An Iraqi policeman was killed and seven others wounded in clashes with protesters loyal to prominent Shia cleric Moqtada al-Sadr who had gathered in Baghdad on Saturday to demand political reforms, the interior ministry said.

Hundreds of supporters of Iraqi cleric Moqtada al-Sadr demonstrated in Baghdad Wednesday to demand electoral reform ahead of a planned provincial vote in September.

Thousands of supporters of powerful Shia Muslim cleric Moqtada al-Sadr filled a central Baghdad square on Friday, disregarding government pleas to scrap protests it said would distract from the war against Islamic State.