Al-Qaeda's Syria affiliate captured at least five more US-trained rebel fighters in overnight raids on a village in northwestern Syria, a monitoring group said on Tuesday.
"Between Monday and Tuesday, Al-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 jihadists already captured at least eight rebels from the same US-backed unit last week, the Observatory reported.
According to Abdel Rahman, late on Monday, Al-Nusra 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 Al-Nusra was "hunting down" US-backed rebels in both Idlib province, where Qah is located, and neighbouring Aleppo province.
A 54-strong rebel unit, trained and equipped by the Pentagon, was inserted into Aleppo province in mid-July as part of US plans to forge a moderate force for the campaign against the Islamic State group.
But despite Al-Nusra's fierce hostility to the rival jihadists of IS, the unit soon came under attack by the Al-Qaeda loyalists.
They seized eight of its men in Aleppo province on 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 US air strikes and at the cost of at least five dead.