More than 600 members of Iraq’s Mahdi Army are in detention awaiting prosecution, the US military announced in a statement late on Monday – the latest indication that operations against the radical Shia militia have been stepped up and that Prime Minister Nouri al-Maliki has withdrawn political protection from the group.

The statement is unusual in that it detailed the number of operations against specific organisations and seems intended to show that there is a new emphasis on neutralising the Mahdi Army. It said that in the past 45 days, the US-led coalition and Iraqi security forces had carried out 52 operations focused primarily against the militia, compared to 42 targeting Sunni insurgents.