BAGHDAD: A day after more than 40 protesters were killed by security forces, Iraq’s prime minister announced Friday that he would submit his resignation to parliament, a step that carried uncertainty for the entire government and stirred fears of a possible political crisis.

The move by Adel Abdul-Mahdi came 13 months after he took office and followed calls by Iraq's top Shiite cleric for lawmakers to withdraw support. At least four protesters were killed in the hours after the announcement in continuing violence in Baghdad and southern Iraq.

Word of the planned resignation triggered celebrations by anti-government protesters who have been camped out for nearly two months in Baghdad’s Tahrir Square. Young men and women broke into song and dance under the sparkle of fireworks crackling from every corner of the plaza, the epicenter of their leaderless protest movement, which seeks an end to sectarian government and election and anti-corruption reforms.

But amid the mirth, protesters said Abdul Mahdi’s decision was a single victory in the long and difficult war aimed at dismantling the post-2003 political system, a common refrain among demonstrators.

“The political system will replace him with someone exactly the same,” said Taif, a 39-year-old protester, as jubilant demonstrators waved flags behind. “Until this sick system is destroyed, we won’t leave.”

On the street near the teeming square, another protester named Mortada, 21, watched the fanfare from a distance. “We want true electoral reforms. We want real change,” he said. “It’s not one man, it’s the whole system that needs to resign.”

Both Taif and Mortada declined to give their full names, fearing retaliation.

Protesters in the teeming square sang Iraq’s national anthem. One man held up a sign: “I cry blood for our martyrs.”

Nearly 400 people have been killed in the bloody crackdown on protests since Oct. 1, most of them young demonstrators who were shot or hit by exploding tear gas canisters fired by security forces.

In a statement, Abdul-Mahdi said he "listened with great concern" to Grand Ayatollah Ali al-Sistani’s sermon and made his decision in response to the cleric’s remarks.

"I will submit to parliament an official memorandum resigning from the current prime ministry so that the parliament can review its choices,” he said. Abdul-Mahdi was appointed Iraq’s fifth prime minister since 2003 as a consensus candidate following months of political wrangling between rival political blocs.

If accepted when put to vote, Abdul-Mahdi’s resignation would signal a return to square one in those slow-moving negotiations, Iraqi officials and experts said.

He would be the second prime minister in an Arab country to be forced out by mass protests recently. In Lebanon, the resignation of Prime Minister Saad Hariri a month earlier, on Oct. 29, led to further political gridlock and uncertainty.

Abdul-Mahdi’s rise to power was the product of a provisional alliance between parliament’s two main blocs — Sairoon, led by cleric Moqtada al-Sadr, and Fatah, which includes leaders associated with the paramilitary Popular Mobilization Units headed by Hadi al-Amiri.

In the May 2018 election, neither coalition won a commanding plurality that would have enabled it to name the premier, as stipulated by the Iraqi constitution. To avoid political crisis, Sairoon and Fatah forged a precarious union with Abdul-Mahdi as their prime minister.

Now, with his resignation, unresolved disputes between the coalitions threaten to re-emerge, two Iraqi officials said.

Abdul-Mahdi had alluded to this challenge implicitly in earlier statements, saying he would resign, but only if an alternative candidate was found for the premiership.

Officials also questioned Abdul-Mahdi’s decision to submit his resignation via the more time-consuming route of parliament, requiring MPs to vote, rather than sending it directly to the president, who has the power to accept it immediately and demote the government to caretaker status until a new one is formed.

An Iraqi official said one of two things could happen: “There’s going to be a lot of horse-trading going on, or it could be paralysis, and nothing changes.” The official spoke on the condition of anonymity because officials were not authorized to speak to media.

The resignation also creates legal uncertainties as the constitution does not provide clear procedures to guide lawmakers in the event of a premier stepping down, experts said. The key issue was how long Abdul-Mahdi’s government could maintain caretaker status in the event of protracted political negotiations.

“To my understanding there is no clause (in the constitution) that says how long he can remain in the post once his resignation is accepted,” said Sajad Jiyad, the managing director of Bayan Center, an Iraq-based think tank.

The federal Supreme Court might have to step in, he added, if the caretaker government stays for too long and if parliamentary blocs are unable to come to an understanding.

In his weekly Friday sermon delivered via a representative in the holy city of Najaf, Al-Sistani said parliament, which elected the government of Abdul-Mahdi, should “reconsider its options” - a clear sign he was withdrawing his support for the prime minister. His comments prompted political parties to issue calls for the government to step down.

Forty protesters were shot dead by security forces in Baghdad and the southern cities of Najaf and Nasiriyah on Thursday, in a sharp escalation of violence that continued Friday.

In Baghdad, one protester was shot dead by security forces on the historic Rasheed Street, a recent focus of clashes, near the strategic Ahrar bridge partly occupied by demonstrators.

Six protesters were killed by live ammunition and tear gas in the city of Nasiriyah when demonstrators attempted to enter the city center to resume their sit-in, security and hospital officials said. Security forces had fired live rounds the previous day to disperse protesters from two key bridges, killing 31 people.

A former oil and finance minister and an ex-vice president, the 77-year-old Abdul-Mahdi was seen as a political independent when he took the post in October 2018. He was Iraq’s first prime minister from outside the Dawa party in 12 years.

His administration’s policies were characterized by small gains to improve the day-to-day lives of Baghdadis. He moved his offices out of Baghdad’s highly secure Green Zone on the first day of his term, saying he wanted to bring his government closer to the people, while removing wartime cement barriers that had closed Iraqis off from much of the city.

In the halls of power in Baghdad, his office worked behind the scenes to streamline the administration and improve decision-making. But the effects of those efforts were not visible to an Iraqi public impatient for reform.

Abdul-Mahdi was also often caught in the middle of rising tensions between the U.S. and Iran, with many perceiving his government and certain staffers as being close to Tehran. Reducing Iraq’s reliance on Iranian electricity imports to meet consumer demand was a key concern of Washington.

Protesters widely reject growing Iranian influence over Iraq state affairs. In Baghdad on Friday, demonstrators gathered around the historic Rasheed Street near the strategic Ahrar Bridge and burned the Iranian flag, chanting “Iran out!”