Iraqi forces launched a sweep through the western desert to flush out remaining Daesh terrorists Thursday, an operation the prime minister has said will spell the group's "final defeat" in the country.

"The Iraqi army, the federal police and the Hashed al-Shaabi (Popular Mobilization paramilitary units) this morning began clearing the Al-Jazeera region straddling Salaheddin, Nineveh and Anbar provinces," the head of Joint Operations Command, General Abdelamir Yarallah said in a statement.

The arid, sparsely populated wastelands between the Tigris and Euphrates rivers are the last refuge of the terrorists in Iraq after troops and paramilitaries ousted them from both valleys and all urban areas.

"The objective behind the operation is to prevent remaining Daesh groups from melting into the desert region and using it as a base for future attacks," army colonel Salah Kareem said.

Iraqi Prime Minister Haider al-Abadi said Tuesday that Daesh had been defeated from a military perspective but he would only declare final victory after Daesh terrorists were routed in the desert.

Iraqi forces on Friday captured the border town of Rawa, the last remaining town under Daesh control, signaling the collapse of the group's "caliphate" proclaimed after it overran much of Iraq's north and west in 2014.

Iraqi army commanders say the military campaign will continue until all the frontier with Syria is secured to prevent Daesh from launching cross border attacks.

"We will completely secure the desert from all terrorist groups of Daesh and declare Iraq clean of those germs," said army Brigadier General Shakir Kadhim.

Once the desert operations end, Abadi is expected to officially announce the final victory over Daesh in Iraq, said official sources.

Army officials said troops advancing through sprawling desert towards the Syria border are facing landmines and roadside bombs placed by retreating terrorists.

"We need to clean scattered villages from terrorists to make sure they no longer operate in the desert area with Syria," said army Lieutenant colonel Ahmed Fairs.

Iraqi military helicopters provided cover for the advancing troops and destroyed at least three vehicles used by Daesh terrorists as they were trying to flee a village in the western desert, said the army officer.

Daesh's self-declared caliphate collapsed in effect in July, when U.S.-backed Iraqi forces captured Mosul, the group's de facto capital in Iraq, after a grueling battle that had lasted nine months.

Driven also from its other bastion in Syria's Raqqa, Daesh has since been gradually squeezed into an ever-shrinking pocket of desert straddling the Syria-Iraq frontier by a range of enemies that include most regional states and global powers.

The group's leader, Abu Bakr al-Baghdadi, is believed to be hiding in the stretch of desert which runs along the border of both countries.