The operation, dubbed "Will of Victory", began early Sunday morning and would push to clear the remote territory between the provinces of Salahaddin, Nineveh and Anbar, a statement by the military said.

Iraqi armed forces, paramilitary units of the Shiite-dominated Hashed al-Shaabi, tribal groups and US-led coalition warplanes were all taking part, according to the statement.

Iraq formally declared victory against the Islamic State group in late 2017, a few months after ousting the jihadists from their seat of power Mosul, the capital of Nineveh province.

The group lost their last sliver of territory in Syria -- a small desert hamlet near the Iraqi border -- in March.

But IS sleeper cells have managed to keep up hit-and-run attacks in desolate parts of Iraq, targeting government checkpoints, public infrastructure and local officials.

Iraq's security forces have targeted IS in several coalition-backed operations in recent months, including in the rugged Hamrin region north of Baghdad.

In May, they armed tribal forces in several dozen villages in Nineveh province to defend themselves against insurgent attacks.