Turkish-backed forces fighting Kurdish militias in north-east Syria have been accused of committing war crimes, with acts of brutality surfacing on mobile phone footage. The UN has warned that Turkey could be held responsible for the actions of its allies, while Turkey has promised to investigate. Bearded men shout "Allahu Akbar [God is the Greatest]". One captures the scene on his smartphone and says: "We are mujahedeen [holy warriors] from Faylaq Al-Majd [Glory Corps] battalion." In the background are the corpses of Kurdish fighters. Further away, a group of men plant their feet on a woman's bloodied body. One says she is a "whore". The gruesome footage is much like that produced by the ultra-violent Islamic State (IS) group. Yet the men in this video are not IS militants, but rather fighters for a rebel alliance known as the Syrian National Army, trained, equipped and paid for by a Nato member, Turkey. They are under the command of the Turkish army. The video was filmed on 21 October in northern Syria. The woman beneath the fighters' feet is Amara Renas, a member of an all-woman unit of Kurdish fighters, the YPJ, a force that played a significant role in defeating IS in Syria. Amara was killed in the recent Turkish assaults against Kurdish forces in Syria. On 9 October the Turkish army and pro-Turkish Syrian rebels attacked the Kurdish-led Syrian Democratic Forces (SDF), shortly after Donald Trump announced the US would pull troops out of Syria. SDF fighters had been a highly effective and trusted ally of the US-led coalition and led the defeat of IS on the ground. The group says it also provided intelligence that led to the killing last week of IS leader Abu Bakr al-Baghdadi.