Final assault on Raqqa to begin, says US-backed commander

A final assault on the Islamic State (IS) group's last line of defence in its former Syrian capital Raqqa should begin on Sunday night, a field commander for the US-backed forces operating there said. 

The loss of IS's remaining streets and buildings in Raqqa following its defeat in Iraq's Mosul this year and its retreat from large areas of territory in both countries would mark a big moment in the battle to destroy the militant group.

At the height of its power two years ago, IS ruled over millions of people from northern Syria to the outskirts of Iraq’s capital Baghdad, but it has since endured a series of losses under attack from many sides.

The assault on militants in the centre of Raqqa will focus on the area around the city's stadium and would attempt to surround it, Ardal Raqqa, a field commander in the Syrian Democratic Forces (SDF) in western Raqqa, told Reuters on Sunday.

For three years Raqqa was the de facto Syrian capital of IS's self-declared caliphate, a centre of operations where it oversaw the management of much of eastern, central and northern Syria and planned attacks abroad.

Now it is hemmed into a small area in the city centre that includes the stadium, the National Hospital and a roundabout where IS once displayed the heads of its enemies.

The group has lost most of its territory to the predominantly Kurdish SDF and to a rival offensive by Syria's army and allied forces this year, and has fallen back on the fertile Euphrates valley area downstream of Raqqa.

The army and its allies reached the city of Deir Ezzor in September after a months-long offensive across the Syrian desert, and have since then pushed down the Euphrates towards the border with Iraq.

On Sunday, a Syrian military source said they had encircled IS militants in the city of al-Mayadin, one of the militants’ last strongholds in the area.

"Units of our armed forces with the allied forces continue their advance on a number of fronts and axes in Deir Ezzor and its countryside ... and encircle Daesh [Islamic State] terrorists in the city of al-Mayadin," the military source said.

However, the militant group has still been able to launch a series of effective counter attacks against the Syrian army in the central desert region over the past week, putting pressure on the main supply road to Deir Ezzor from the west. 

Rival offensive

Syrian President Bashar al-Assad is backed in the war by Russia, Iran and Shia militias including Lebanon's Hezbollah, and its campaign against IS has mostly been on the west bank of the river.

The US-backed SDF campaign has mostly been on the east bank, where Raqqa is located, and it has also advanced downstream to hold areas opposite Deir Ezzor. The US and Russia have put in place channels to lessen the risk of fighting between the rival offensives they back.

US officials have previously said that IS had relocated some of its diminished command and propaganda structures to al-Mayadin as it was forced from territory elsewhere.