A suicide bomber has attacked a government-backed armed group north of Baghdad, killing at least 19 people in an apparent attempt by Sunni fighters to stoke unrest against Iraq's Shia prime minister, Nouri al-Maliki.
Police said the bomber had infiltrated a meeting of Sahwa tribal fighters on Monday and detonated his explosives as they were gathering to pick up salaries in Taji, a town 20km north of the capital.
The seventh suicide bombing in a month was part of a surge in violence a year after US troops pulled out of the country, where Shia, Sunni and ethnic Kurdish factions still struggle over how to share power.
"We got a call they had been a huge blast on the Sahwa headquarters in Taji. The Sahwa were there to collect their pay," said local police commissioner Furat Faleh. "When we rushed to the hall ... people were lying bleeding all around and cash was scattered in pools of blood."
No claim of responsibility
The Sahwa or "Sons of Iraq" are former Sunni fighters who rebelled against al-Qaeda in the Sunni heartland province of Anbar at the height of the US-led war and helped American troops to turn the tide of the conflict.
No group claimed responsibility for Monday's attack, but al-Qaeda's affiliate, Islamic State of Iraq, has vowed to take back ground lost to American and US forces, and has urged Iraqi Sunnis to rise up against Maliki's government.
A suicide bomber and gunmen killed at least 33 people in a huge blast at the police headquarters in the disputed northern oil city of Kirkuk on Sunday.
Maliki has been struggling to end mass protests by Sunni Muslims against what they see as marginalisation of their sect since the fall of Saddam Hussein and the rise of Iraq's Shias.
The Sunni unrest and the violence are compounding fears that the war in neighbouring Syria, where Sunni rebels are battling to topple President Bashar al-Assad, could undermine Iraq's own delicate sectarian and ethnic balance.