By Sylvia Westall and Tom Perry
BEIRUT (Reuters) - Al Qaeda's Syria wing said on Friday it had detained members of a Syrian rebel group who had just returned from U.S. training, in a direct challenge to Washington's plan to train and equip insurgents to combat the hard-line Islamic State group.
In a statement that appeared to contradict comments from the Pentagon, Nusra Front said the men it was holding had entered Syria several days prior and had been trained under the supervision of the Central Intelligence Agency.
It described them as agents of America and warned others they should abandon the program. It also said a U.S.-led coalition had mounted air strikes against Nusra Front positions during fighting between the group and the rebels.
Syrian opposition sources and a monitoring group said earlier this week that Nusra Front had detained the leader of the U.S-trained rebel "Division 30" and a number of its members. The Pentagon cast doubt on the reports on Thursday, saying no members of the "New Syrian Force" had been captured or detained.
"We warn soldiers of (Division 30) against proceeding in the American project," Nusra Front said in a statement distributed online. "We, and the Sunni people in Syria, will not allow their sacrifices to be offered on a golden platter to the American side."
Nusra Front, one of the most powerful insurgent groups in northern Syria, has a record of crushing rebel groups that have received support from Western states, including the Hazzm movement that collapsed earlier this year.
The latest incident highlights the difficulties the United States faces in its efforts to train and equip rebels to fight Islamic State, which is a rival of Nusra Front.
U.S.-TRAINED FIGHTERS ELIMINATED: NUSRA
Nusra Front said it had eliminated fighters who the United States had sought to embed in Syria in the past two years.
It said Division 30 had coordinated air strikes with the U.S.-led alliance against its positions, a reference to fighting between the sides on Friday. The strikes "left a number of martyrs and wounded in our ranks", the statement said.
The Syrian Observatory for Human Rights monitoring group said on Friday that warplanes believed to be part of the U.S.-led alliance had bombed Nusra Front positions in an area near the town of Azaz, north of Aleppo city.
It said at least 18 Nusra Front fighters had been killed in the air strikes and ground fighting, while seven rebel fighters had died in the clashes.
Nusra Front attacked Division 30 and other rebels overnight, rebel groups and the Observatory said on Friday, escalating tension between rival insurgents near the Turkish border.
The fighting points to one of the major complications facing U.S. and Turkish plans to jointly sweep Islamic State militants from northern Syria.
On Friday, Division 30 said Nusra Front fighters attacked its headquarters at 4.30 a.m. (0130 GMT) in the area near Azaz. Five members of Division 30 were killed as they held off the attackers, it said.
Another rebel group in the area said it had also clashed with Nusra Front. Jaish al-Thuwar, a rebel alliance formed earlier this year, said in a statement posted on Facebook (NASDAQ:FB) on Friday that four of its members and at least eight attackers had been killed.
Nusra Front, which Washington has designated a terrorist organization, last year routed the Syria Revolutionaries Front led by Jamal Maarouf, viewed as one of the most powerful insurgent leaders until his defeat.
It was also instrumental in the demise of the U.S.-backed Hazzm Movement, which collapsed earlier this year after clashing with the Nusra Front in the northwest.
Washington and Ankara this week announced their intention to provide air cover for Syrian rebels and jointly sweep Islamic State fighters from a strip of land along the border, with U.S. warplanes using bases in Turkey for strikes.