A Mehdi Army fighter heads for cover in the southern city of Basra during a second day of fighting with Iraqi security forces that has claimed more than 40 lives.
The Shia Mehdi Army is led by the young firebrand cleric Moqtada Sadr, whose supporters - pictured here in a Basra residential area - are known as Sadrists.
With the city under curfew, many of the normally bustling streets are virtually deserted. Prime Minister Nouri Maliki has given militants 72 hours to lay down their arms.
Fighting across several Basra districts has been stoked by a variety of militias and criminal gangs, say correspondents, and the violence has spread to other parts of Iraq.
Iraqi security forces have also been battling Shia militants in Baghdad. Five Iraqi civilians have been killed and many more injured.
Jamila market in the Iraqi capital's sprawling Shia slum of Sadr City was destroyed overnight as Mehdi Army fighters clashed with American and Iraqi soldiers.
Iraqi children flash the victory sign next to debris from a US armoured personnel carrier hit overnight by a roadside bomb in Sadr City.
A Sadrist carries a copy of the Koran and an olive branch during a rally in the Shia holy city of Karbala. The writing on the placard reads: "Reward good deeds with good deeds."
A man in Baghdad with prayer beads before a poster of Moqtada Sadr's father, another Shia cleric, who was assassinated in 1999.