Mass grave found as US-backed forces close on final IS bastion

US-backed Syrian Democratic Forces say they have discovered a mass grave containing dozens of bodies near the ISIS hold-out of Baghouz, in the country's east.

A member of US-backed Syrian Democratic Forces (SDF), stands guard at the Ya'arubiya border crossing with Iraq in northeastern Hasakah province, northern Syria. Source: AP

A mass grave containing the bodies of dozens of people possibly enslaved by IS has been found in territory recently seized by the US-backed Syrian Democratic Forces.

Many of the bodies found in the Baghouz area were those of women.

"They were slaughtered," SDF commander Adnan Afrin said on Thursday. Most had been decapitated.

The SDF was still trying to confirm if the bodies belonged to members of the Yazidi sect.

Thousands of members of the minority sect from Iraq were forced into sexual slavery by the jihadists when they surged across the border in 2014 and seized swathes of territory.

Syrian refugees gather as they wait to leave Beirut to return home to Syria. Source: AP

More than 3000 other Yazidis were killed in an onslaught the United Nations later described as genocidal, which prompted the first US air strikes against the so-called Islamic State.'

Thousands more fled on foot and many of them remain displaced more than four years later.

The SDF, the main Kurdish led-partner of the US-led coalition against IS in Syria, has been trying to evacuate thousands of civilians in Baghouz before storming it or forcing the surrender of the remaining jihadists, who the SDF has said are mostly foreigners.

It said earlier on Thursday it had freed 24 of its fighters held by IS in Baghouz but gave no details about how they were recovered.

A member of US-backed Syrian Democratic Forces (SDF), stands guard at the Ya'arubiya border crossing with Iraq in northeastern Hasakah province, northern Syria. Source: AP

Thousands of people of many nationalities have streamed out of the final shred of land in recent weeks, an exodus of both its supporters and victims, surpassing initial estimates and delaying an end to the battle.

Residents say hundreds of Arab civilians have been killed in US-led coalition air raids since the campaign began several months ago with many of their homes in villages and towns east of the Euphrates River levelled.

The United Nations on Thursday expressed concern about the plight of thousands whom residents say are tribal Arabs in a camp in al Hol in northeastern Hasaka province.

Coalition forces have pushed IS jihadists out of their last holdfast in Syria. Source: AP

Many of those fleeing, nearly all of them women and children, were being taken into custody by the SDF.