Rebels cut main IS supply route between Syria and Turkey: Report

An Arab-Kurdish alliance backed by US air attacks severed the Islamic State (IS) group's main supply route to Turkey on Friday, after encircling a key militant-held town in northern Syria.

IS has been under pressure on various fronts in the parts of Syria and Iraq where it established its self-declared "caliphate" in 2014, and the group lost control Friday of the vital supply artery when Arab-Kurdish forces surrounded Manbij.

"The Syrian Democratic Forces cut off the last road from Manbij to the Turkish border on Friday morning," the UK-based Syrian Observatory for Human Rights said.

IS still controls territory along the Turkish border with secondary roads to the frontier but these are more dangerous and difficult to access, Observatory head Rami Abdel Rahman said.

He said: "For the jihadists to reach the Turkish border from Raqqa, they now have to take a route that is more dangerous because of government troops nearby and Russian air strikes."

Russia launched air strikes in support of President Bashar al-Assad's government in Syria in September.

More than 130 Islamic State group fighters have been killed in the US-backed offensive on Manbij, the Observatory said on Thursday.

US-led coalition air strikes supporting the assault by Kurdish and Arab fighters, launched on 31 May, have also left 30 civilians dead, according to reports.

Thousands of residents have fled Manbij - held by IS since 2014 - but fighters who evacuated their families stayed to defend the town, the Observatory said.

About 20,000 people are still living in the town, which had a pre-war population of about 120,000 - mostly Arabs, but about a quarter Syrian Kurds.

Earlier this week the Syrian Democratic Forces (SDF), backed by air strikes by the US-led coalition, cut the road north out of Manbij to the IS-held border town of Jarabulus, which the militants had used as a transit point for fighters, money and weapons.

The SDF also blocked the road south out of Manbij heading to IS's de facto capital of Raqqa.

This follows a push last month by the SDF on two fronts from the north of Raqqa province towards Manbij and in direction of the IS-held town of Tabqa on the same vital supply line further south.

Government troops backed by Russian air strikes have also pushed an offensive to the southwest of Tabqa.

Moscow and Washington - despite backing different sides in Syria's five-year conflict - have both focused efforts on fighting the group.