Islamic State mounts fierce defence of besieged Syrian bastion

Militants responded to an operation launched by a force comprised of a Kurdish-Arab alliance by detonating a wave of suicide and car bombings.

On Friday, two suicide attacks and five car bombings rocked the southwestern suburbs of Manbij where the Syrian Democratic Forces (SDF) has been stationed since advancing last week.

Tens of thousands of civilians have been reportedly trapped inside Manbij after the alliance encircled the transit town on Friday in a major blow to the Islamic State group.

Hundreds managed to escape the besieged city with help by the US-backed SDF who accuse IS of using civilians as human shields.

"On Friday, six members of the same family were killed when they were targeted by jihadists while fleeing," Rami Abdel Rahman, head of the monitoring group Syrian Observatory said.

Figures from last week showed at least 223 IS fighters and 28 SDF troops had been killed – as well as 41 civilians in coalition air raids – since the alliance offensive against Manbij began on May 31, according to the Observatory.

Manbij lies at the heart of the last stretch of IS-controlled territory along Turkey's border.

The siege has severed a key supply route for IS fighters, money and weapons from the Turkish border to the group's de facto Syrian capital of Raqqa city.

Syria's war has killed 280,000 people and displaced millions since it erupted with the brutal repression of anti-government protests in 2011.

IS has come under attack on several fronts since declaring a cross-border "caliphate" in Syria and Iraq in 2014.