The funeral had been for Mudher al-Shallal al-Araki, who was killed in a roadside bombing near his family's home in the restive city of Baquba, north of Baghdad, the previous evening, according to a police colonel and Dr Hussein al-Tamimi from a nearby hospital.
The blast struck at the graveyard where the procession, which included relatives and members of the family's tribe, was due to bury the body.
Araki had been a fighter in the Sahwa, the militia formed of tribesmen that, from late 2006 began siding with US forces against their co-religionists in al Qaeda, helping turn the tide of Iraq's insurgency.
Baquba is the capital of confessionally-mixed Diyala province, which remains one of the least stable areas in the country and regularly suffers deadly violence.
It is the latest in a protracted surge in bloodshed, Iraq's worst since 2008 that has forced authorities to appeal for international help in combatting militancy just months before general elections.
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