Baghdad, Iraq: Iraqi paramilitaries launched an operation Saturday to retake the town of Tal Afar from the Islamic State group and cut jihadist supply lines from Mosul to Syria, a spokesman said.

Forces from the Hashed al-Shaabi, a paramilitary umbrella organisation dominated by Iran-backed Shiite militias, have largely been on the sidelines since the operation to retake Mosul from the Islamic State group was launched last week.

"The operation aims to cut supplies between Mosul and Raqa and tighten the siege of (IS) in Mosul and liberate Tal Afar," Hashed spokesman Ahmed al-Assadi told AFP, referring to IS's main strongholds in Iraq and Syria.

Assadi said the operation aimed to retake the towns of Hatra and Tal Abta as well as Tal Afar, Assadi said.

The operation could bring the fighting perilously close to the ancient city of Hatra, located northeast of the town of the same name, a UNESCO world heritage site that has already been vandalised by IS.

The involvement of Shiite militias in the Mosul operation has been a source of contention, although some of the Hashed's top commanders insist they do not plan to enter the largely Sunni city.

Iraqi Kurds and Sunni Arab politicians have opposed their involvement, as has Turkey, which has a military presence east of Mosul despite repeated demands by Baghdad for the forces to be withdrawn.

Relations between the Hashed and the US-led coalition fighting IS are also tense, but the paramilitaries enjoy widespread support among members of Iraq's Shiite majority.

Tal Afar was a Shiite-majority town before the Sunni extremists of IS overran it in 2014, and its recapture is a main goal of Shiite militia forces.

IS overran large areas north and west of Baghdad in 2014, but Iraqi forces have since regained significant ground and Mosul is the last big city held by the jihadists in the country.