Fighting escalates in Syria

A final assault on Islamic State's last line of defence in its former Syrian capital Raqa should begin yesterday night, a field commander for the US-backed forces operating there said as fight against jihadists intensifies across Syria.

The loss of Islamic State's remaining streets and buildings in Raqa following its defeat in Iraq's Mosul this year and its retreat from swathes of territory in both countries, would mark a big moment in the battle to destroy the jihadist group.

At the height of its power two years ago Islamic State 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.

For three years Raqa was the de facto Syrian capital of Islamic State'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.

Meanwhile, Turkish military vehicles crossed the Syrian border into Idlib yesterday, a local resident and a local rebel said, after Ankara announced an operation by rebel groups in the area, which is controlled by rival jihadist alliance Tahrir al-Sham.

The operation follows a deal between Turkey and Syrian President Bashar al-Assad's allies Russia and Iran to impose a "de-escalation" zone in Idlib and surrounding areas to reduce warfare there, an agreement that did not include Tahrir al-Sham.

In another front, Syria's army and its allies have encircled Islamic State in the city of al-Mayadin, southeast of Deir al-Zor, in eastern Syria, a Syrian military source said yesterday.

Al-Mayadin is one of the last strongholds of Islamic State as it falls back upon the fertile area downstream of Deir al-Zor in the Euphrates valley and launches counter attacks in the central desert after losing swathes of territory this year.

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