Army spokesman Yahya Rassoul said the incident took place in a region near the Syrian border, where jihadist sleeper cells are believed to be present.

He said the suspects died as troops surrounded them but there were no casualties among government forces.

Local officials said the suspects were killed as they were trying to attack troops in the village of Qayrawan, south of the mountainous region of Sinjar which borders Syria.

Fighters of the US-backed Syrian Democratic Forces on Saturday pronounced the death of the nearly five-year-old IS "caliphate" which once stretched across a vast swathe of Syria and Iraq.

Their victory was hailed as a major landmark in the battle against the jihadists but there have also been numerous calls for "vigilance" with many saying the fight is far from over.

Top SDF commander Mazloum Kobane on Saturday warned that a new phase had begun in anti-IS operations and appealed for sustained assistance from the US-led coalition to help smash "sleeper cells".

Diehard jihadists continue to have a presence in mountainous or desert regions between Syria and Iraq, which had declared victory over IS in December 2017.

In Iraq some of these regions remain inaccessible to security forces.