A suicide bomber has killed at least nine people and injured 29 more southwest of Baghdad, Iraqi police says.
The bomber attacked government-backed Sunni militia members lining up to be paid, in the town of Radwaniya.
The Sunni militia fighters, known as Sahwa or Sons of Iraq, were once allied with al-Qaeda, but turned against the militant group in 2006.
The Sahwa are credited with helping to reduce the overall levels of violence in Iraq since they joined the US military and government forces in the fight against al-Qaeda.
But they have been frequently targeted by militants and have recently complained about harassment from government troops as a political vacuum continues following inconclusive elections in March.
Sunni insurgents have sought to exploit the deadlock created by a failure of Sunni, Shia and Kurdish factions to agree on a new coalition government.
There are also fears that the political uncertainty could hinder the planned withdrawal of all US combat troops from Iraq by the end of August, in preparation for a full military departure by 2012.
