Fewer than 3,000 IS fighters left in Iraq, Syria: coalition

IS is currently fighting for survival in the handful of sparsely populated pockets of territory it still holds, a far cry from the vast swathes of ground it captured in 2014.

"Current estimates are that there are less than 3000 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.

Iraqi government troops backed up by air strikes from the US-led coalition are pressing an offensive to wipe out the jihadists' last foothold in the desert.

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

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saying at the end of November that more than 400 Marines who helped in the recapture of Syrian city Raqa were being withdrawn.