Syria's ambassador to the United Nations told the Security Council on Friday that a day earlier, 40,000 people had been able to leave the besieged Damascus suburb of Eastern Ghouta.
Previous estimates of the number of people who were able to flee as a Russian-backed Syrian regime assault on the sprawling semi-rural area continued had ranged between 12,000 and 20,000.
Ambassador Bashar al-Jaafari, speaking after UN peace envoy Staffan de Mistura said the conflict is escalating despite a ceasefire call, said Syrian and Russian forces had opened "corridors" for civilians.
"They arrived in centers set up by the Syria government and the Syrian Red Crescent -- temporary shelters equipped with all necessary means to take care of them," the envoy told the council hearing.
Separately, UN Secretary-General Antonio Guterres raised alarm over the exodus from Ghouta, which is under a month-old bombardment by Syrian and Russian forces, and from Afrin, under Turkish assault.
"I profoundly regret that resolution 2401, concerning the cessation of hostilities throughout Syria, has not been implemented," he said, referring to the February 24 UN vote to demand a ceasefire.
"I urge all parties to the conflict to fully respect international humanitarian and human rights law and guarantee the protection of civilians," he continued, in a statement from his office.
"Any evacuation of civilians must be safe, voluntary, and in strict accordance with protection standards under international humanitarian and human rights law," Guterres said.
De Mistura, who briefed the council before it headed into a closed-door session to debate the crisis, also painted a bleak picture of a failed ceasefire and escalating humanitarian tragedy.
But, speaking by videolink from Brussels where he has just undergone eye surgery, he did point to one corner of the conflict where Russia has at least demonstrated it can organize a local truce.
In Douma, the northernmost of the opposition-controlled enclaves in Eastern Ghouta, Russian officials negotiated a ceasefire with the Jaish al-Islam rebel force that has held for six days, he said.
"We hope it will continue, notwithstanding engagements between government forces and Jaish al-Islam in other areas, outside of Douma," he said, however warning that even in Douma, the truce is "fragile."
"It need not be this way. Negotiations in Douma do show that there is a way to create the conditions that can advance the implementation of your resolution 2401," he told the council.
De Mistura said Douma represented "one bit of good news" among the bad and that the UN has not been able to mediate contacts between Russia and another rebel force active in Ghouta, Ahrar al-Sham.