Islamic State claimed responsibility on Wednesday for a deadly gun attack near the Iraqi town of Tarmiya.
A security source had told Reuters that militants killed eight unarmed civilians in the assault 25 km (15 miles) north of Baghdad on Tuesday.
Islamic State said it killed 22 people, describing them all as members of a government-backed Sunni Muslim tribal force called the Tribal Mobilization Forces.
"Clashes with light and medium weapons took place and led to the death of 22 apostates and the wounding of 10 others," the Sunni militant group said in a statement.
Iraq declared victory in December over Islamic State, which had seized control of nearly a third of the country in 2014. But the group continues to carry out attacks and bombings in Baghdad and other parts of the country.