'Fewer than 3,000 IS fighters' left in Iraq, Syria

There are fewer than 3,000 fighters from the Islamic State group left in Iraq and Syria as the jihadis cling to the remnants of its self-styled caliphate, the US-led coalition battling the militants said on Tuesday.

Iraqi forces announced the launch of a major operation in November to flush remaining Islamic State group fighters out of the western desert near the border with Syria.

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

"Current estimates are that there are less than 3,000 Daesh fighters left - they still remain a threat, but we will continue to support our partner forces to defeat them," coalition spokesman Ryan Dillon wrote on Twitter, using an alternative acronym for IS.

In Syria, IS have faced separate onslaughts by forces backed by Russia and the US in Deir az-Zour province and now control just a tiny sliver of the region along the Euphrates river.

Last month, Syria's army and its allies ousted the Islamic State group from its last urban stronghold in Albu Kamal in the eastern province of Deir az-Zour.

IS seized large areas of both Syria and neighbouring Iraq in a lightning 2014 campaign, but this year has lost much of the territory it once held.

The US has already begun winding down its forces deployed to fight IS, with the coalition saying at the end of November that more than 400 marines who helped in the recapture of Syrian city Raqqa were being withdrawn.