The Syrian government and its Russian backers say they've recaptured more than 90 percent of the key opposition stronghold of eastern Aleppo.
Much of the ancient city, which was once the country's largest, has been leveled. Just this week tens of thousands fled rebel-held areas to the relative calm of the government-controlled west. Russia put the number of those leaving at 50,000 in just two days — 20,000 on Saturday alone.
But the nightmare is far from over.
While Russian officials announced that Syrian troops had suspended their offensive to allow civilians to flee on Saturday, activist-run Syrian Observatory for Human Rights said heavy clashes were still underway. Meanwhile, some residents of eastern Aleppo were reportedly fleeing deeper into opposition-controlled neighborhoods.
And on Friday, the United Nations warned that hundreds of men and boys had disappeared after leaving areas controlled by the opposition.
Human rights workers said they feared that they had been detained by the regime.
"You have a great number of people that are then exposed to reprisals of different kinds, including being picked up, taken to detention centers, interrogated and tortured," Philip Luther, the head of Amnesty International's Middle East program, told NBC News.
Amnesty alleges that since 2011, thousands have died in Syrian detention centers while tens of thousands more have been tortured. Some inmates die of starvation, and many are beaten, raped and given electric shocks.
The U.N. also raised worries over reports that opposition armed groups could be treating citizens like "pawns" — abducting and sometimes killing residents who tried to leave besieged areas.
Western diplomats, meanwhile, were struggling to find a way to save an estimated 100,000 who are still trapped.
Secretary of State John Kerry on Friday called what is happening in Aleppo and Syria in general "the worst catastrophe since World War II."
"It is unacceptable. It is horrible," he said.
Rebels are in retreat throughout Syria. Pressure mounted on Assad in 2015 when rebels — some of whom are backed by the U.S. and its allies — captured the northwestern province of Idlib, but then Russia joined the war in September 2015 and tipped the balance.
Assad, who is also supported by Iranian forces and Lebanon's Hezbollah militias, has beaten back the rebellion that started off as a peaceful pro-democracy movement in 2011.
