Iraq's anti-Government protesters have been dealt a major blow, with a popular cleric and political leader withdrawing his support for the months-long demonstrations that have erupted across the Middle Eastern country.

Key points: Powerful cleric and politician Muqtada al-Sadr has withdrawn his support for anti-government protesters

Powerful cleric and politician Muqtada al-Sadr has withdrawn his support for anti-government protesters The cleric had previously urged his militia group to support the protesters

The cleric had previously urged his militia group to support the protesters Experts say the move is designed to make him a kingmaker as Iraq chooses its next PM

Since October 1, at least 500 people have been killed during crackdowns on ordinary Iraqis protesting against government corruption, high unemployment and Iranian influence in Iraqi politics.

On Saturday, another four demonstrators were killed by security forces: three in Nasiriyah and one in Baghdad.

Another 44 were injured in the Iraqi capital.

Previously, protesters had the support of Muqtada al-Sadr — a powerful cleric and Iraqi politician — who had urged his followers and militia to lend support to the protest movement, according to activists.

Mr al-Sadr withdrew his support after most anti-government protesters reportedly did not turn up to an anti-US rally he and his supporters organised, prompting scores of his supporters to pack down their protest camps in Baghdad and in other cities.

Powerful cleric calls protesters 'foreign paid tools'

It is thought Mr al-Sadr's decision is designed to improve his political fortunes. ( Reuters: Alaa al-Marajani )

A spokesperson for the cleric said some protesters insulted those participating in the anti-US rally and even obstructed access to the one in southern Iraq.

Mr al-Sadr said he thought the protesters he broke with were "supporters of me and of Iraq", but has since urged his followers and militia to turn their backs on them.

The dissolution of his support for the protesters comes at a critical time for the country, as its Parliament trying to agree on a consensus candidate to replace outgoing Prime Minister Adel Abdul-Mahdi, who resigned in December amid pressure over the protests.

Ordinary Iraqis have been protesting against government corruption and a stagnant economy. ( AP: Hadi Mizban )

Iraq also has been swept up in US-Iran tensions, after Washington assassinated top Iranian General Qassem Soleimani outside Baghdad's airport — prompting Tehran to fire missiles at Iraqi air bases hosting American and coalition troops in retaliation.

After the US killing, the Iraqi Parliament approved a non-binding resolution calling on foreign forces to leave the country. It remains unclear if the US and its allies will heed that call.

Mr al-Sadr's show of force on the street is one way to ensure the next premier brings a pro-[al-Sadr] agenda to government, analysts said.

"For him, it's about political capital and relevance," Sajad Jiyad, managing director of the Bayan Centre, a Baghdad-based think tank, said.

"Al-Sadr has shown that he can bring large numbers to the street. By asking his supporters to withdraw yesterday night [he] is showing that he is the force behind the protests and can put an end to them if necessary."

Mr al-Sadr has rejected every proposed prime ministerial candidate put forward by a rival bloc, Fatah.

Protesters rebuilding incinerated tents

Supporters of Mr al-Sadr dismantled their tents on his orders. ( AP: Hadi Mizban )

With Mr al-Sadr's cover gone, many in the four-month-old movement feared the worst.

"We are all alone now," said Mustafa, 24, who asked that his full name not be used because he feared reprisals.

Following Mr al-Sadr's decision on Friday, riot police set fire to a protest camp early on Saturday in a central square in the southern city of Basra, two activists said.

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"This is considered a betrayal by the al-Sadr bloc … There will be no peace after what has happened in Basra last night," activist Nakeeb Lueibi said.

Protesters feared security forces would enter Tahrir Square.

"[Al-Sadr's statement] gave the green light for the Government to suppress the demonstrations," Husanien Ali, a 35-year-old protester, said.

Others said they would remain resilient.

"We called for more people to join us in Tahrir," said Noor, a protester who only gave her last name because she feared reprisal.

"We are rebuilding the tents."

Protesters continued to occupy bridges leading to Baghdad's heavily fortified Green Zone.

ABC/AP