Kiran Nazish

Special for USA TODAY

ISTANBUL — Desperate Syrians trapped in besieged eastern Aleppo see death on their doorstep and describe what may be their final moments in social media posts and telephone calls.

"At home waiting for the inevitable fate that Allah wills," Salah Ashkar, 28, said in a telephone call, his voice quaking as Syrian government forces moved in to reclaim the last portions of Aleppo held by rebel forces.

"I can't see what is happening in street, but I hear bombs approaching," Ashkar, a graduate of the University of Aleppo in finance and banking, told USA TODAY. "There is no safe building left. Possible that we (will be) exposed to bombing any moment."

Nearly half a million killed, and Syria civil war isn't over

Ashkar, who has been posting videos of the carnage, said Syrian troops were executing civilians on the streets, including women and children. Similar allegations have been reported by other residents to the United Nations and activists in Aleppo.

Syrian rebels reached a cease-fire deal Tuesday to evacuate from eastern Aleppo in an effective surrender, as Russia declared all military action had stopped, the Associated Press reported.

Retaking Aleppo, once Syria's largest city and commercial capital, would be a major win for President Bashar Assad in his 5-year-old civil war, which has turned in his favor since Russia's military came to his support this year.

'Everyone is dying. I will soon die, too'

"Where are our supporters?" asked Radhwan Salem, 60. "Believers in humanity, I don't understand how can the entire world watch this and do nothing. Oh, God, help us."

"We are not afraid of death, and we have no demands," said Salem. "We only want freedom for us, and to rob it from Assad. I have lived my life in this city, I raised my children and their children here. I am ready to give my life defending my family."

Abdulla Saleem, 39, a doctor who is living in the bombed out remains of a building, said via WhatsApp, "They are killing everyone. ... My friends are doctors, who were providing the only possible medical care to the injured. Now they are butchered. Everyone is dying. I will soon die, too."

"All the doctors at Al-Hayat (field medical clinic) have been executed," said Abu Zubair, 29. "My friends have given their blood. They have fought the fight they chose, for the humanity."

"My wife was killed separately in a bomb, but before that my children were killed in an attack," said Zubair. "They died because we couldn't pull them out of the rubble."

"My friends will defend Aleppo to the death," said Mohsin Salem, 33. "To the world outside of Aleppo, to the United States, I don't want to say anything more than stand by Aleppo. And if we all die, remember us."

Rupert Colville, a spokesman for the U.N. human rights office, told reporters in Geneva on Tuesday that the office received reports that pro-government forces entering former rebel enclaves in eastern Aleppo killed at least 82 civilians, including 11 women and 13 children.

"We're filled with the deepest foreboding for those who remain in this last hellish corner," Colville said.

Damascus confirmed the evacuation deal and the U.N. envoy for Syria, Staffan de Mistura, told the AP in a text message that the safe withdrawal of people from the besieged area was “imminent.”

The U.N. later called for immediate access to eastern Aleppo to confirm that Russia stopped military operations and to monitor the evacuation.

De Mistura told reporters after an emergency Security Council meeting that armed groups are still estimated to control about 2 square miles in eastern Aleppo. He said the U.N.’s main concern is the up to 50,000 civilians still believed to be in that part of the city, the AP reported.

Bashar al-Ja’afari, Syria’s ambassador to the U.N., denied any mass executions or revenge attacks, but added it was Syria’s “constitutional right” to go after “terrorists,” a reference to all opposition fighters.

“Aleppo has been liberated from terrorists and those who toyed with terrorism,” he said. “Aleppo has returned to the nation.”

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The White Helmets, a volunteer civil defense and rescue service operating in Aleppo and other aid groups appealed for the international community to put in place a humanitarian corridor to allow civilians to flee, Reuters said.

Marianne Gasser, the Red Cross’ head of delegation in Syria, appealed Tuesday to the parties involved “to put humanity ahead of military objectives."

“We stand ready to oversee the implementation of any mutual agreement that puts civilians first. We cannot urge this strongly enough: this must happen now,” she said in a statement.

Contributing: Jane Onyanga-Omara in London