BEIRUT, Lebanon — Russian officials said Thursday that the Syrian Army had stopped combat operations in the divided city of Aleppo in order to evacuate civilians, but residents of the rebel-held enclave reported that after a day of intense bombardment, fighting was ongoing.

Russia’s foreign minister, Sergei V. Lavrov, said that the pause would allow for 8,000 civilians to be evacuated, after forces loyal to the Syrian government recaptured three-quarters of the territory rebels had held for four years.

Mr. Lavrov, who spoke on the sidelines of a meeting of foreign ministers in Germany, did not offer specifics on an evacuation plan. But civilians inside the remaining rebel-held districts of eastern Aleppo were in a state of panic after a day in which rescue workers said 150 airstrikes had killed at least 50 people and residents said they were unable to flee because of the intense combat.

Residents said by telephone that they could hear drones and tank fire, and that they feared government forces were closing in on the few neighborhoods still held by rebels. Several said they had not heard of evacuation offers and begged to be told of any chances to escape.

At the United Nations, the agency’s envoy for Syria, Staffan de Mistura, told reporters he could not verify whether the fighting had stopped, or whether civilians were being allowed to evacuate, and pressed the government authorities to let them leave safely and with protection from United Nations staff.

His remarks came after a closed-door session of the Security Council, in which Mr. de Mistura said government forces could take control of the remaining rebel-held parts of Aleppo by the end of the year and that rebel forces should be allowed to leave the city safely, if they wished, according to diplomats present.

The United States which has backed elements of the opposition to President Bashar al-Assad of Syria, cautiously welcomed Mr. Lavrov’s remarks.

Josh Earnest, the White House spokesman, called it “an indication that something positive could happen but we’re going to have to wait and see,” adding, “Our approach to the situation has been to listen carefully to what the Russians say, but scrutinize their actions.”

Pleas for help from eastern Aleppo escalated on Thursday, with doctors warning that they could no longer provide more than first aid. Some residents reached via telephone and text message were fleeing from the front lines into the center of the shrinking enclave, while others stayed near the edges hoping to evacuate but complaining that the combatants would not pause to let them escape.

The recapture of most of the rebel-held part of Aleppo by the government marks a potential turning point in Syria’s war, which began in 2011 with largely peaceful street protests demanding political change and evolved into armed conflict after government crackdowns.

Mr. Assad told Al Watan, a pro-government newspaper, that victory in Aleppo “doesn’t mean the end of the war in Syria. It is a significant landmark toward the end of the battle, but the war in Syria will not end until terrorism is eliminated,” he said, referring to insurgents.

The International Committee for the Red Cross said it had evacuated more than 140 civilians from Aleppo’s old city that had been retaken by the government; mainly residents of a home for older people, and recovered the bodies of 11 people who had died for lack of medical care.

The White Helmets organization, which rescues people from bombing sites and has financing from Western countries, issued a statement saying that it feared a massacre, and asking to evacuate its volunteers, who have been accused by the Syrian government of colluding with terrorists. “If we are not evacuated, our volunteers face torture and execution in the regime’s detention centers,” the statement said. “We have good reason to fear for our lives.”

Bombs containing chlorine, banned as a weapon by international law, fell on the front line near Kalasseh neighborhood, sickening about 30 people, the White Helmets and

Salem Abul Nasser, a dentist, said he had hoped for a few quiet hours after Mr. Lavrov spoke and had fallen asleep, only to be wakened when a corpse of a man newly killed on the front line and another person suffering from apparent chlorine inhalation were brought to his clinic.

Showing the body over an online video chat, he broke into tears, saying, “I was hoping it would be a real cease-fire, now I’m deeply disappointed and pessimistic. The shelling resumed now, I can hear it.”

The United Nations humanitarian chief, Jan Egeland, expressed frustration that aid deliveries had not been approved by the Syrian government in November — when front lines were more stable — and that now the United States and Russia, as well as the Syrian combatants, could not agree on a plan to deliver aid and evacuate civilians who want to leave.

Russia’s Foreign Ministry issued an angry and sarcastic response to a statement from six Western countries a day earlier that had warned of a humanitarian catastrophe in Aleppo. The ministry said that Russia was providing aid to residents it said had been liberated from a terrorist occupation.

“If you are ready to render aid to residents of Aleppo, let us know where this aid is located,” the statement said. “And if you just don’t have any aid, letters and empty promises won’t fill bellies of Aleppo’s residents!”

Mr. Lavrov’s comments on a halt in fighting came on the eve of new efforts, albeit entirely symbolic, at the United Nations to press for a pause in fighting. Led by Canada, the United Nations General Assembly is scheduled to vote on a draft resolution that calls for a “cessation of hostilities” for an undefined period of time and that allows humanitarian aid to be delivered. It would have no force of law.

The Russian ambassador, Vitaly I. Churkin, described it as “not very effective.”