BEIRUT -- Fighters loyal to al Qaida have opened up a new offensive against a U.S.-backed rebel group that once escorted U.S. Sen. John McCain into northern Syria, according to Internet postings and news accounts.
The Islamic State of Iraq and Sham, an al Qaida affiliate whose fighters come from a wide range of nationalities, launched attacks on the Northern Storm Brigade late Tuesday night, hitting Northern Storm positions in a string of villages along Syrias border with Turkey.
The Islamic State, whose leader has sworn allegiance to al Qaida head Ayman Zawahiri, claimed the attacks in statements posted on the Internet in which it accused Northern Storm of not keeping the terms of a cease-fire that halted fighting between the two groups last week in the Syrian city of Azaz.
Meanwhile, Muslim scholars in Aleppo reportedly have declared Northern Storm a criminal group, a designation that is discouraging other Syrian rebels from coming to the groups aid. Reports indicated the Islamic State fighters clearly had the upper hand and would take most of the border crossings that they didnt already control.
The fighting between the Islamic State and Northern Storm is a setback for U.S. plans to assist so-called moderate rebels so that they become dominant in northern Syria. Northern Storm is affiliated with the Supreme Military Command, the rebel military faction through which the United States and its allies have said they would funnel all military supplies to the rebels.
But the U.S.-backed rebels so far have shown little ability to resist the al Qaida-linked fighters. The Islamic State handily routed Northern Storm fighters last week in clashes in Azaz before a third rebel faction negotiated a cease-fire that kept Northern Storm from being wiped out.
As part of that agreement, Islamic State spokesmen claimed Wednesday, the Northern Storm was to surrender its heavy weapons. When it did not, the Islamic State launched its offensive.
There are very fierce clashes on the outskirts of Azaz. ISIS cut all roads leading to Turkey and the situation is very tense, the Reuters news agency quoted one unidentified rebel as saying.
Antipathy between the two groups runs deep. One Internet forum sympathetic to the Islamic State said that the Northern Storm had been nicknamed the Shabiha of McCain, a reference to pro-regime militias in Syria that are often blamed for mass killings as well as to McCains May trip to meet with the head of the Supreme Military Command, defected Syrian Gen. Salim Idriss.
Beyond the obviously embarrassing optics of an American-backed rebel unit being routed by the much better equipped, organized and disciplined Islamic State fighters, the battle calls into question the safety of nine Lebanese Shiite Muslim hostages that Northern Storm captured last year. The safety of the so called Nine Pilgrims, who claimed to be touring Shiite religious shrines in northern Syria, has become a critical issue in neighboring Lebanons battle for stability while its population is torn between both sides in the Syrian civil war.
Aymeen Tamimi, a Great Britain-based analyst and fellow with the Middle East Forum in Philadelphia, predicted that the decision by religious scholars in Aleppo to declare the Northern Storm a criminal group would be critical in the fighting, keeping other rebels from helping.
ISIS military might is far greater, Tamimi said.
After a year of easy gains against an unpopular regime, Syrias rebel movement has seen progress in overthrowing President Bashar Assad stall as both Syrians and outside backers of the rebels have become uncomfortable with the growing radical Islamic nature of the revolt. Last week, at least five groups affiliated with the Supreme Military Command were among a dozen or so groups that signed an alliance with another al Qaida affiliate, the Nusra Front, and rejected working with the Turkey-based Syrian Opposition Coalition, the civilian group the United States and its allies recognize as the legitimate successor to Assad.
The Islamic State was not included in that alliance, but rebel groups have made it clear that they will continue to coordinate operations with it. Islamic State fighters have been key to rebel victories.
The possibility that the Islamic State would end up capturing the nine Shiite pilgrims from the Northern Storm also is worrisome.
As for the Lebanese pilgrims, they will either be slaughtered or held hostage as bargaining chips, Tamimi said.