The militants were disguised in government-sanctioned paramilitary forces uniforms
Iraq: ISIL says it killed 10 policemen
ISIL has claimed responsibility for abducting and killing 10 policemen in north Iraq.
Pictures posted online by the extremist group showed eight men in civilian clothing on their knees in an open area with militants pointing rifles at their backs. Another picture showed two men flanked by militants brandishing knives.
Two police officers said on Sunday that only nine troops from the federal police were kidnapped on Tuesday by militants disguised in government-sanctioned paramilitary forces uniforms.
They said the slain troops were on leave when the extremists stopped their SUV taxi at a checkpoint on a highway between the northern Kirkuk and Salaheddin provinces.
Both spoke on condition of anonymity as they were not authorized to brief reporters.
The kidnapping took place just days after a series of deadly attacks by ISIL sleeper cells in Kirkuk claimed the lives of 25 people, including civilians and fighters.
The attacks indicate that despite no longer controlling large swathes of territory, ISIL is far from a spent force in Iraq, undermining the government's claim that the group has been defeated.
The violence threatens to disrupt Iraq's upcoming elections in May, as any sustained effort to kill civilians, soldiers or police would undermine Prime Minister Haider Al Abadi's campaign.