Soldiers, civilians and members of the government-backed Sahwa militia of Sunni ex-insurgents were among the casualties in the Amiriya district of the Iraqi capital, the source said.

Overall violence in Iraq has dropped sharply since the height of sectarian war in 2006-07.

But political uncertainty following an inconclusive March 7 election has fueled a spike in violence over the past two months.

Iraq's new parliament is due to convene on Monday, but a government has yet to be formed.

The cross-sectarian Iraqiya alliance led by former Prime Minister Iyad Allawi narrowly won the vote with the heavy backing of voters from Iraq's once-dominant Sunni minority.

But he faces being outmaneuvred by the main Shiite blocs of incumbent Prime Minister Nuri Al-Maliki and firebrand anti-US cleric Moqtada Al-Sadr, who have announced a tie-up.

Coalition talks threaten to drag into the next phase of US military withdrawal, with the US working to formally end combat operations by Sept. 1, cutting its military force from just under 90,000 to 50,000.

Iraqi security forces and members of the Sahwa militia appear to be bearing the brunt of the violence. The Sahwa, or Sons of Iraq, are former Sunni insurgents who switched sides to fight Sunni Islamist Al-Qaeda and helped turn the tide of the war.

(Editing by Elizabeth Fullerton)