BEIRUT — The siege in Aleppo is almost over.
Advances by Syrian government forces and their allies have squeezed the fighters and civilians remaining in rebel-held parts of the city into a sliver of territory, said spokesmen for the government and the opposition forces Monday. The last civilians caught in the shrinking antigovernment enclave issued panicked calls for help.
It appeared increasingly likely that the government would soon gain control of the whole of Aleppo, the largest city in Syria.
That would be a turning point in the civil war, cementing government rule over all of Syria’s most important cities and forcing the opposition and its backers to reckon with whether their movement, especially the armed rebellion, has failed.
It also raises questions about how an increasingly confident President Bashar Assad will govern a deeply wounded and divided country where war still rages.
Assad’s recent military successes have depended heavily on help from Russia, Iran, and the Iranian-backed Lebanese Shi’ite militant group Hezbollah, which are reviled by many of Assad’s Sunni opponents and viewed with unease even by his supporters, because of their growing power in the country.
Large areas of Aleppo and other cities and towns have been reduced to rubble by the fighting. And rebel forces, Kurdish militias, and Islamic State fighters are still operating in large areas of the north and east of the country.
That has been vividly clear in recent days, with Islamic State fighters advancing in the desert city of Palmyra and its ancient ruins as the government focused on Aleppo.
For civilians trapped behind the battle lines in Aleppo, though, more urgent questions loomed. Time appeared to be running out to strike a deal to allow them to evacuate.
Rebel and opposition leaders want evacuees to be given an option to go to territory they control. Many of the remaining civilians refuse to go to government-held territory because they are afraid they would be jailed and tortured there. Others say the bombardment in their districts is too intense to allow any escape.
There were also reports in state media of rebel shelling of government-held areas.
According to the Russian government, Assad’s main foreign backer, more than 100,000 people have fled from the rebel enclave to government-held areas, and 2,200 rebel fighters have surrendered. At least 13,000 people have fled in the past 24 hours, it said.
But there are still believed to be thousands of civilians trapped in districts that have been bombarded for more than 24 hours, while the army and its militia allies seized most of the southern part of the city.
“An important call in the name of civilians to help them,” Abdelkafi al-Hamdo, a teacher and antigovernment activist, said in a text message to a group of journalists. “Stop bombing. Take them out.”
The situation was so desperate, residents said, that it was unclear whether rebels and civilians there could even hold a meeting to decide whether to surrender and evacuate.
“Believe me, no one rejects the safety evacuation,” one resident, Yasser Abu al-Joud, said in a text message to the journalists’ group. “All of us are waiting, dying now in the last neighborhoods.”
Hisham al-Skeif is a civilian member of the local council that had tried to govern the rebel-held areas of Aleppo, which once included half the city. Skeif expressed frustration that although international officials were in contact with rebel leaders, no one appeared to be talking directly to the trapped civilians.
“All the political activists and the media, the relief workers, the unarmed, we are about 1,000, including our families,” he said. Though the government has said it would offer amnesty to anyone who surrenders, “if the regime entered, we will be slaughtered,” he said. “Of course everybody is negotiating with those who are armed, but we are not armed.”
“The armed can defend themselves, but we can’t,” he added.
Hamdo said in a series of text messages that families in Aleppo were “waiting death together.”
“People are running, don’t know where,” he wrote. “People are under the rubble alive, and no one can save them. Some people are injured in the streets, and no one can go to help them [because] the bombs are always on the same place.”
Some rebel leaders have said that the United States, which backs some rebel groups, had sent them a proposal that would allow evacuees their choice of destination, under security guarantees from Russia. But trust has eroded to such an extent that the rebels have yet to respond.
Syrian and Russian officials say the offensive in Aleppo will continue until rebels surrender or die.
“The issue of withdrawing militants is the subject of separate agreements,” Sergei Ryabkov, the Russian deputy foreign minister, told the Ria news agency Monday. “This agreement has not yet been reached, largely because the United States insists on unacceptable terms.”
The sticking point for months has been a dispute between Russia and the United States over what to do about fighters linked with Al Qaeda who are among the rebel groups in eastern Aleppo.
The United Nations estimates that about 10 percent of the 8,000 rebel fighters in the city belong to an Al Qaeda-linked group, the Levant Conquest Front. The rebels and their international backers say the figure is much lower; the government says it is much higher.
Before the government broke through the rebel defenses, the UN was proposing that the Levant Conquest Front leave Aleppo in exchange for three main broad concessions from the government side: an end to bombardment; protection and aid for remaining civilians; and some form of local administration for rebel areas.
But the government rejected any form of self-government, saying that it would “reward terrorists,” while the rebels rejected versions of the deal that did not include it.