The Nusra Front meanwhile released a video showing one of the captured rebels saying that the men in the faction known as Division 30 were trained in Turkey by US officers and sent back to Syria with money and weapons.
The fighting came a few days after the US and Turkey announced the outlines of a deal to help rebels push the Islamic State group back from a strip of territory it controls along the Syrian-Turkish border, replacing it with more moderate rebels backed by Washington and Ankara.
Abdurrahman and Marea said Division 30 had less than 60 fighters and that on Friday alone the group lost five fighters and 18 others were wounded.
A representative of Division 30 did not respond to written questions sent to the group's Facebook account.