Beirut — Airstrikes killed and burned scores of people on Friday in a rebel-held suburb of Damascus, rescue workers and a monitoring group said, as the Syrian army closed in amid a growing exodus from the area.

Activists and doctors from the town of Kafra Batna shared photographs of charred bodies — some mangled in the wreckage, others wrapped in rugs and blankets. The Syrian-American Medical Society, a nonprofit that supports medical facilities in the area, said 61 people were killed in the attack.

Rescue workers and conflict monitors said Russian planes carried out the airstrikes. Russia’s Defense Ministry denied involvement.

The rebel-held enclave of Eastern Ghouta has long defied Syrian President Bashar al-Assad’s attempts to restore his rule over the Damascus area, and his army, backed by Russia, has pushed in recent weeks to divide the area into three pockets of opposition control.

Thousands of civilians have escaped to government territory since Thursday. Many of them, dazed and exhausted, have told traumatic stories of oppression by the rebels who controlled their towns.

But thousands more have run in the other direction, fearing vengeance by the security forces they resisted during Syria’s 2011 uprising.

The Syrian Observatory for Human Rights, a Britain-based monitoring group, said on Friday that 80 people were killed across the enclave. Siraj Mahmoud, a spokesman for the White Helmets rescue group, said the victims had been stockpiling food for their families.

In a video briefing on Friday at the United Nations Security Council, Staffan de Mistura, the U.N. envoy for Syria, described fresh allegations that incendiary weapons were being used against civilians in Eastern Ghouta, as well as “disturbing” reports that munitions have been laced with chlorine, a chemical weapon.