Baghdad (AFP) - Twelve protesters were killed Monday after supporters of cleric Moqtada Sadr stormed the government palace in Baghdad's Green Zone as the powerful Shiite leader said he was quitting politics.
Shots were fired in the fortified area which houses government buildings as well as diplomatic missions, an AFP correspondent said, as tensions soared amid an escalating political crisis that has left Iraq without a new government, prime minister or president for months.
Medics told AFP that 12 Sadr supporters had been shot dead and 270 other protesters were hurt -- some with bullet wounds and others suffering tear gas inhalation.
Witnesses said earlier that Sadr loyalists and supporters of a rival Shiite bloc, the pro-Iran Coordination Framework, had exchanged fire.
The Framework condemned an "attack on state institutions", urging the Sadrists to engage in "dialogue".
The army announced a nationwide curfew from 7:00 pm (1600 GMT), as security forces patrolled the capital.
Caretaker Prime Minister Mustafa al-Kadhemi ordered an investigation into the casualties, adding that "security or military forces, or armed men" were prohibited from opening fire on protesters.
"Our security forces are responsible for protecting protesters.Any violation in this regard will be subject to legal accountability," his office tweeted, adding that he urged people to abide by the curfew.
Calling the developments "an extremely dangerous escalation", the United Nations Assistance Mission in Iraq (UNAMI) urged "all" sides to "refrain from acts that could lead to an unstoppable chain of events".
"The very survival of the state is at stake," it warned.
The United States also urged calm amid the "disturbing" reports of unrest in Baghdad.
Protests spread to other parts of the country, with Sadr followers storming government buildings in the cities of Nasiriyah and Hillah south of Baghdad, an AFP correspondent and witnesses said.
'Definitive retirement'
Iraq has been mired in political deadlock since legislative elections in October last year, due to disagreement between Shiite factions over forming a coalition.
Shortly after he made his surprise declaration, Sadr's followers burst into the Republican Palace, where cabinet meetings are usually held.
Inside the opulent palace, protesters lounged in armchairs in a meeting room, some waved Iraqi flags and took photographs of themselves, and others cooled off in a swimming pool in the garden.
Sadr -- a grey-bearded preacher with millions of devoted followers, who once led a militia against American and Iraqi government forces -- announced earlier on Twitter he was stepping back from politics.
"I've decided not to meddle in political affairs.I therefore announce now my definitive retirement," said Sadr, a longtime player in the war-torn country's political scene, though he himself has never directly been in government.
He added that "all the institutions" linked to his Sadrist movement will be closed, except the mausoleum of his father, assassinated in 1999, and other heritage facilities.
His latest statement came two days after he said "all parties" including his own should give up government positions in order to help resolve the political crisis.
His bloc emerged from last year's election as the biggest, with 73 seats, but short of a majority.In June, his lawmakers quit in a bid to break the logjam, which led to the Coordination Framework becoming the largest bloc in the legislature.
Hamzeh Hadad, from the European Council on Foreign Relations (ECFR), said it was "not clear" what Sadr's strategy was.
"Whatever it does mean, in typical Sadrist fashion, there is always backtracking expected," Hadad said.
"The second, and more terrifying thought on this is that he is giving his followers the green light to do whatever they like."
Millions of followers
Sadr's supporters have been calling for parliament to be dissolved and for new elections, but on Saturday the cleric said it was "more important" that "all parties and figures who have been part of the political process" since the 2003 US-led invasion "no longer participate".
"That includes the Sadrist movement," he said.
Over the years, the chameleon-like Sadr has taken various positions and then reversed them.
Sadr's supporters have for weeks been staging a sit-in outside Iraq's parliament, after storming the legislature's interior on July 30, to press their demands.
They were angered after the Coordination Framework nominated a candidate they saw as unacceptable for prime minister.
The Framework wants a new head of government to be appointed before any new polls are held.
Kadhemi had earlier this month convened crisis talks with party leaders, but the Sadrists boycotted.
