Islamist rebels were trying to wrest control Sunday of a pair of besieged pro-government towns in northern Syria, according to opposition and loyalist accounts.
Fighters from Al Nusra Front, Al Qaeda's Syrian affiliate, launched Grad missiles and mortar rounds as part of an assault that began Saturday on the towns of Nubul and Zahra, northwest of Aleppo. Rebels say they seized control of the southern and eastern entrances to the communities, home to more than 40,000 people, mostly Shiite Muslims.
The two towns are islands of government support in a region where largely Sunni Muslim rebels have seized broad swaths of territory. Insurgents have laid siege to Nubul and Zahra for more than two years.
The latest offensive against the two towns could be an attempt to draw the attention of pro-government forces and relieve pressure on Aleppo, which has been split between government and opposition control since July 2012. Rebel commanders fear that advancing loyalist forces could eventually gain sufficient ground to encircle the entire opposition-held sector of Aleppo.
According to opposition activists, Nubul and Zahra provide a steady flow of government recruits and have become major staging grounds for government attacks in the north.
Nubul and Zahra also occupy a strategic position. The towns are situated just west of Handarat, a settlement along a major highway and rebel supply corridor between Aleppo and nearby Turkey. Government forces have been fighting to seize Handarat and cut off the opposition from weapons and other supplies flowing in from neighboring Turkey.
The battle for the Shiite outposts of Nubul and Zahra highlights how the Syrian conflict, now in its fourth year, has taken on a distinct sectarian character.
News outlets affiliated with Al Nusra Front released high resolution photos depicting what were described as rebel tanks and weaponized pickup trucks, operating amid fierce clashes on the southern edge of Zahra. One image purports to show a bearded figure giving a pep talk to comrades "before attacking the Shiites."
Syria's small Shiite minority has generally remained loyal to the government of President Bashar Assad. Assad is a member of the Alawite sect, an offshoot of Shiite Islam.
Syrian rebels are overwhelmingly Sunni, the dominant sect in Syria. Al Nusra Front, like its Al Qaeda parent organization, is a Sunni group. Many Syrian opposition fighters view Alawites and Shiites as apostates.
Assad's secular government has maintained a strong base of support among Alawites, Christians and other Syrian minorities who fear persecution should Sunni Islamist rebels seize power.
Among the forces reported to be defending Nubul and Zahra are elements of Lebanon's Hezbollah, a Shiite organization that has dispatched thousands of militiamen to fight alongside pro-government forces in Syria.
It was unclear whether other rebel groups, such as brigades affiliated with the U.S.-backed Free Syrian Army, were participating in the assault on the two towns. FSA fighters have often been allied with Al Nusra combatants. But Al Nusra has recently attacked some FSA units in northern Syria in a bid to consolidate its control.
Nubul and Zahra reportedly factored in a complex deal brokered by the United Nations in May that allowed thousands of opposition fighters to evacuate from war-ravaged Homs city, in central Syria. As part of the agreement, rebels besieging the towns were supposed to allow in regular shipments of food and other essential goods. But the government officials and humanitarian groups say aid access to the towns has remained irregular.
Bulos is a special correspondent.