"Between Monday and Tuesday, The Nusra Front seized at least five rebels from Division 30 in the village of Qah, near the Turkish border," Syrian Observatory for Human Rights chief Rami Abdel Rahman said.
The terrorists already captured at least 8 rebels from the same U.S.-backed unit last week.
According to Abdel Rahman, late Monday, Nusra Front stormed a camp for internally displaced people in Qah, where the rebel fighters had taken refuge.
"Five fighters were seen captured but there may be more."
The Observatory chief said Nusra Front was "hunting down" U.S.-backed rebels in both Idlib province, where Qah is located, and neighboring Aleppo province.
A 54-strong rebel unit, trained and equipped by the Pentagon, was inserted into Aleppo province in mid-July as part of U.S. plans to forge a “moderate force” for the campaign against ISIS.
"According to Abdel Rahman, late Monday, Nusra Front stormed a camp for internally displaced people in Qah, where the rebel fighters had taken refuge."
But despite Nusra Front's fierce hostility to the rival terrorists of ISIS, the unit soon came under attack by the Al-Qaeda loyalists.
They seized eight of its men in Aleppo province Wednesday, the Observatory said, in a report that drew a denial from the Pentagon.
On Friday, they launched an assault on Division 30's headquarters in the province that was only repulsed with the help of U.S. airstrikes and at the cost of at least five dead.