Aleppo Fighting Flares Up as Syria Insurgents Attack

BEIRUT, Lebanon — The fiercest fighting in months raged in the divided Syrian city of Aleppo on Friday, as newly reorganized insurgents carried out a new offensive on government-held areas.

Two insurgent coalitions — a new one that includes the Nusra Front, Al Qaeda’s branch in Syria, and one formed in May by local factions long active in Aleppo — attacked simultaneously from several directions, unleashing hundreds of rockets and shells. Government forces hit back with shelling and airstrikes, and civilians came under fire from both sides, according to witnesses and statements from the warring parties.

The stakes are high for all sides. For President Bashar al-Assad, losing his foothold in Aleppo, Syria’s industrial and economic capital and its largest city before the war, would signal that the government could not meaningfully project power beyond its strongholds stretching from the Mediterranean coastal mountains to Damascus, the capital. For the insurgents, the fight tests whether they can reprise their seizure earlier this year of another provincial capital, Idlib, where they executed an unusually coherent battle plan through a newly created, unified operations center.

But Aleppo is a greater challenge for them: The government and its allies, the Lebanese group Hezbollah and Iraqi Shiite militias, are likely to fight harder. And the Islamic State jihadist group is trying to drive rival insurgents out of core territory east of city.

Just hours after the battle began late Thursday, rifts were already evident between insurgent groups — apparently centering on who would rule Aleppo and how, as the new coalition including the Nusra Front declared it would rule with other factions according to Islamic law. That raised the specter of infighting among insurgent groups if they manage to drive out government forces.

The fighting also underscored the lack of progress from international leaders in finding a political solution to the war, which has lasted four and a half years and claimed more than 230,000 lives, driven millions from their homes, and destroyed much of the storied old city of Aleppo. Less than a year ago, the United Nations special envoy, Staffan di Mistura, had pinned hopes for reviving talks on a proposed freeze in fighting in Aleppo; the idea never gained traction.

Turkey, a fierce opponent of Mr. Assad, sent reinforcements to its borders as the fighting intensified, raising speculation of an imminent intervention. But the prime minister, Ahmet Davutoglu, told a Turkish television channel that the country aimed only to protect its borders.

Footage posted online by Syrian insurgents showed explosions like fireworks and the flash of tracer bullets over Aleppo at night, and heavy smoke at dawn over the Zahra neighborhood, which insurgents said they had wrested by morning from government hands.

Much of the fighting in Aleppo has been with ground-to-ground projectiles that are fired into civilian areas. Coupled with government airstrikes, that has meant that civilians are again bearing the brunt of the fighting, amid the strain of life in a city divided into government and rebel zones by a deadly buffer zone. Death tolls in the latest fighting were impossible to confirm, but each side said that civilians had been killed and claimed to have killed scores of the others’ fighters.

As the fighting started, the Nusra Front and its close ally Ahrar al-Sham, a large Islamist faction, declared the formation of a new coalition called Ansar al-Shariah — which can be translated as Supporters of Islamic Law — that included several other factions coordinated through a shared operations room.

In a video statement, its leaders declared that their aim was “the liberation of Aleppo and its countryside,” after which they would work with other factions on a “joint covenant” to rule the city “according to the rules of Sharia.”

But the new formation did not include some of the main groups that have held eastern Aleppo since insurgents seized it in 2012. Those groups include some that United States officials have at times deemed moderate enough to receive aid, and had previously organized a joint operations room called Fatah Halab, or Conquest of Aleppo.

They, too, joined the battle alongside the new coalition, with the commander, Yaser Abdulrahman, declaring in a video, “In retaliation for the massacres committed by the regime against our people in Aleppo, we won’t stop till the liberation of the whole of Aleppo, God willing.”

The two groups appeared to work together, and some activists and insurgents said they remain allies at least for the short term but divided into two separate coalitions as a gesture to satisfy the United States and its allies, which object to aiding groups that work directly with the Nusra Front.

An Islamist activist who shares often reliable information about the various factions on Twitter, using the name Mzamjer al-Sham, criticized the formation of Ansar al-Shariah, calling it a sign of fragmentation. He said other factions in Aleppo were preparing to declare yet another operations center, meaning there would be three rival groups.

“The factions in Aleppo disagreed on how to run the city if liberated, so they were divided into three operation rooms,” he wrote.

“Each of them is aiming to liberate the city from the jaws of the pliers,” he added, referring to the government forces and those of the Islamic State, which has clashed in the area with Nusra and a range of other insurgent groups that oppose its self-declared caliphate.

By Friday evening, it was Fatah Halab, the coalition that excludes the Nusra Front, that was claiming victories. Its leaders announced that they had taken over a scientific research center west of downtown.