Reuters) - The Joint Operations Command in Iraq announced a curfew across the country from seven in the evening on Monday until further notice. Reuters reporters said that dozens of young men loyal to Shiite cleric Muqtada al-Sadr clashed with supporters of Iranian-backed groups outside the Green Zone in central Baghdad, which includes government compounds and embassies, and they exchanged stones. Correspondents added that the sound of gunfire was heard in central Baghdad, apparently as a result of shots being fired in the air. The clashes took place hours after al-Sadr announced his withdrawal from politics, prompting his supporters, who have been camping for weeks inside the parliament headquarters in the Green Zone, to demonstrate and storm the main headquarters of the Council of Ministers.