BAGHDAD: Iraqi Prime Minister Adel Abdul Mahdi announced his resignation on Friday after the country’s senior Shiite cleric urged lawmakers to reconsider their support for a government rocked by weeks of deadly anti-establishment unrest.

Violence raged on in southern Iraq, however, killing at least 21 people, and protesters continued a thousands-strong sit-in at Tahrir Square in central Baghdad.

Young, unemployed and unarmed protesters have led calls for a rehaul of a political system they say is endemically corrupt and serves foreign powers, especially Baghdad’s ally Tehran.

The departure of Abdul Mahdi could be a blow for Iranian influence after Iran’s militia allies and its own commanders intervened last month to keep the premier in place despite mass anti-government unrest.

“In response to this (the cleric’s) call, and in order to facilitate it as quickly as possible, I will present to Parliament a demand (to accept) my resignation from the leadership of the current government,” a statement signed by Abdul Mahdi said.

The statement did not say when he would resign. Parliament is to convene an emergency session on Sunday to discuss the crisis.

Grand Ayatollah Ali Al-Sistani earlier urged Parliament to consider withdrawing its support for Abdul Mahdi’s government to stem spiralling violence.

Abdel Mahdi would be the first prime minister to step down since Iraq became a parliamentary system following the US-led ouster of Saddam Hussein in 2003.

Jubilation

Protesters celebrated the imminent departure of Abdul Mahdi, but said they would not stop their demonstrations until the whole of the political class was removed. Violence continued in southern Iraq.

“Abdul Mahdi’s resignation is just the beginning. We’ll stay in the streets until the entire government has gone, and all the rest of the corrupt politicians,” said Mustafa Hafidh, a protester at Baghdad’s Tahrir Square.

“It’s not enough,” said Ali Al-Sayeda, another demonstrator. “We need them all out, root and branch. We can’t let up the pressure.”

"It's our first victory, and we're hoping for many more," shouted one demonstrator in Tahrir, as patriotic tunes blasted from the motorized rickshaws used to ferry casualties from the square.

Nearby, protesters occupying a gutted 18-storey building that has become a symbol of the uprising could be seen dancing and pumping their fists in the air. But despite their joy, many said the premier's resignation did not go far enough.

"We won't leave the square until every last one of those corrupt people resigns," said another demonstrator in a black shirt.

"Weed them all out. Every single one."

Massacre in Nassiriya

Security forces meanwhile shot dead at least 21 people in the southern city of Nassiriya after protesters tried to storm a local police headquarters, hospital sources said. In Najaf, unidentified armed men shot live rounds at demonstrators sending dozens scattering.

Iraqi forces have killed at least 435 people, mostly young, unarmed demonstrators since mass protests broke out on Oct. 1. More than a dozen members of the security forces have also died in clashes.

Iraq’s “enemies and their apparatuses are trying to sow chaos and infighting to return the country to the age of dictatorship ... everyone must work together to thwart that opportunity,” Al-Sistani said.

The US called on Iraqi leaders to address the “legitimate” grievances of protesters. “We share the protesters’ legitimate concerns,” a State Department spokeswoman said.

“We continue to urge the government of Iraq to advance the reforms demanded by the people, including those that address unemployment, corruption and electoral reform,” she said.

The UN's top official in Iraq, Jeanine Hennis-Plasschaert, said the deaths "cannot be tolerated".

The previous day had been one of the bloodiest yet, with 44 demonstrators killed and nearly 1,000 wounded in Baghdad and across the south.

That came after protesters stormed the Iranian consulate in Najaf late Wednesday, accusing the neighbouring country of propping up Iraq's government.

Tehran demanded Iraq take decisive action against the protesters, saying it was "disgusted" by developments.

"We want all the parties to go"

In response, Abdel Mahdi ordered military chiefs to deploy in several provinces to "impose security and restore order" — but the result was the opposite. Men in civilian clothes opened fire at demonstrators, tribal fighters deployed in the streets and military commanders.

As the death toll surged, governors and police chiefs resigned and Abdel Mahdi sacked a senior military commander. On Friday, demonstrators encircled a Nasiriyah police station and torched five police cars.

And in Najaf, where 16 people died the previous day, new clashes erupted between protesters and armed men dressed in civilian clothes. As in Baghdad, demonstrators in the south did not appear satisfied with Abdel Mahdi's resignation.

"Our problem isn't the prime minister -- we want all the parties to go!" one man told AFP in Diwaniyah.

Since October 1, Baghdad and the south have been rocked by the most widespread street unrest in decades, demanding an overhaul of the ruling elite and reforms to root out corruption, end unemployment and improve infrastructure. The demonstrations initially shook Abdel Mahdi, who came to power last October after a strained alliance between the two largest parliamentary blocs, Saeroon and Fatah.

The protests divided them, with Fatah backing the premier while Saeroon leader and firebrand cleric Moqtada Sadr called for him to resign. But they closed ranks around the cabinet following a deal brokered by top Iranian commander Qasem Soleimani.

The tide turned again this week, culminating with Sistani's dramatic intervention. For weeks, the 89-year-old cleric had called for restraint and urged parties to get "serious" about reform. But he ramped up his demands on Friday.

"The parliament, from which this current government is drawn, is asked to reconsider its choice in this regard," he said in his weekly sermon. Within minutes, Saeroon as well as MP and former premier Haider al-Abadi had called for a vote of no-confidence.

The Fatah bloc called for "the necessary changes in the interests of Iraq".

Parliament is set to meet on Sunday and if it drops its support for the government, the cabinet would remain in place as caretakers until the president names a new premier. Iraq's constitution, drafted in 2005, does not include a provision for the resignation of the premier, so his intention to submit a letter to parliament would trigger a no-confidence vote.

The country is OPEC's second-largest crude producer but one in five Iraqis lives in poverty and youth unemployment stands at 25 percent, according to the World Bank.