The men face charges under Iraq's anti-terror legislation over the killings at Khasfah, a sinkhole in northern Iraq just eight kilometres from Mosul, the former capital of IS's self-declared "caliphate".

"The eight terrorists arrested have admitted to participating in the Khasfah massacre," said Supreme Judicial Council spokesman Abdel Sattar Bayraqdar.

"They participated in the execution of 370 civilians and members of security forces and the arrest of 400 people in Mosul," who were then held in IS jails, he added in a statement.

After IS overran Mosul in 2014, Khasfah became one of Iraq's largest mass graves as jihadists carried out a series of executions at the site.

Witnesses said the victims were blindfolded and had their hands tied behind their backs, before being forced to kneel. They were then shot and pushed into the crater.

More than 300 people, including around 100 foreigners, have been sentenced to death or life in prison by Iraqi courts over their membership of IS, according to judicial sources.

Iraq declared victory in December over the jihadist group, which at its peak controlled nearly a third of the country as well as large swathes of neighbouring Syria.