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.

"There are pockets of Daesh fighters in the northwestern, western, and southwestern parts of Salahaddin province," a media official from the province's military command told AFP, using the Arabic acronym for the Islamic State group.

"Daesh is still present in these areas, and the operations will continue until they are cleared."

Iraq formally declared victory against IS 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 kept up hit-and-run attacks in isolated parts of Iraq, targeting government checkpoints, public infrastructure and local officials.

Security analyst Hisham al-Hashemi said "Will of Victory" was aimed at depriving IS of the resources it uses to carry out those raids.

"It will drain Daesh's logistical support in an area that makes up nearly a quarter of Iraq, by destroying their bases, training camps, depots and tunnels," he told AFP.

He said security forces were seeking to oust an estimated 1,000 IS fighters from the desert regions around Baaj, Rawah and Tharthar.

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 enable populations to defend themselves against insurgent attacks.