BAGHDAD (Reuters) - Iraqi forces launched an operation on Thursday to clear the desert bordering Syria of Islamic State in a final push to rid Iraq of the militant group, the military said.

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Troops from the Iraqi army and mainly Shi’ite paramilitaries known as Popular Mobilisation Forces (PMF) were taking part in the campaign against militants hiding in a large strip of border land, Iraqi military officials said.

“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,” said army colonel Salah Kareem, referring to Islamic State by an Arabic acronym.

Islamic State fighters who ruled over millions of people in both Iraq and Syria since proclaiming their “caliphate” in 2014, have been largely defeated in both countries this year, pushed out of all population centers to empty desert near the border.

Iraqi Prime Minister Haider al-Abadi said on Tuesday Islamic State had been defeated from a military perspective, but he would declare final victory only after the militants were routed in the desert. [nL8N1NR57C]

In the latest operation, Iraqi forces had “purified” 77 villages and exerted control over a bridge and an airport, operations commander Lieutenant General Abdul Ameer Rasheed Yarallah said in a statement. Over 5,800 squared kilometers had been “purified,” he added.

On Friday Iraqi forces captured the border town of Rawa, the last remaining town under Islamic State control. Iraqi army commanders say the military campaign will continue until all the frontier with Syria is secured to prevent Islamic State 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.

LANDMINES, BOMBS

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

“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 militants as they were trying to flee a village in the western desert, said the army officer.

Islamic State’s self-declared caliphate has swiftly collapsed since 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 main bastion in Syria’s Raqqa, Islamic State has since been gradually squeezed into an ever-shrinking pocket of desert straddling the Syria-Iraq frontier, pursued 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.