A group of around 70 US-trained Syrian rebels surrendered a weapons stockpile to jihadist group Jabhat al-Nusra. Fighters from Division 30 surrendered to the al-Qaeda affiliated group after crossing into Syria over the Turkish border.
On Twitter, a man claiming to be an al-Nusra militant and writing under the Abu Fahd al-Tunisi said: "A strong slap for America... the new group from Division 30 that entered yesterday hands over all of its weapons to Jabhat al-Nusra after being granted safe passage.
"They handed over a very large amount of ammunition and medium weaponry and a number of pick-ups." He alleged that the division's commander had promised to denounce the international coalition.
Monitoring group the Syrian Observatory for Human Rights confirmed 75 fighters from the division had crossed into Syria with "12 four wheel vehicles equipped with machine guns and ammunition". US Central Command confirmed around 70 US-trained rebels had crossed into Syria to fight with forces battling jihadist group Islamic State (Isis), according to the Telegraph.
It marks the latest setback for the $500m (£327m) programme to train and equip moderate rebels to take on IS on the ground in Syria, where the group now controls more than 50% of territory despite a year-long US-led air campaign.
In the summer, a group of US-trained rebels were kidnapped by al-Nusra days after being deployed in Syria. Four of those taken were subsequently released. In a recent Senate Armed Services Committee hearing, US Senator John McCain branded the programme a "debacle".