Al-Qaida-linked rebels launched an assault on a regime-held Christian mountain village in the densely populated west of Syria and new clashes erupted near the capital, Damascus, on Wednesday — part of a brutal battle of attrition each side believes it can win despite more than two years of deadlock.

In the attack on the village of Maaloula, rebels commandeered a mountaintop hotel and nearby caves and shelled the community below, said a nun, speaking by phone from a convent in the village. She spoke on condition of anonymity for fear of reprisals.

With the world focused on possible U.S. military action against Syria, there were new signs of fragmentation in rebel ranks, with a small group of jihadis from Russia announcing it has broken away from an umbrella group known as Jabhat al-Nusra.