Syrian Government Has Full Control of Eastern Aleppo, Says Russia's UN Ambassador City has seen months of siege and years of fighting.

 -- Eastern Aleppo has fallen, and military activities there have stopped, according to Russia's United Nations ambassador.

"The Syrian government has re-established control over eastern Aleppo," Vitaly Churkin told the U.N. Security Council on Tuesday.

Residents of eastern Aleppo told ABC News that it is quiet there, with no sounds of battle, but ABC News could not immediately confirm whether fighting has ended.

Churkin earlier said that "all militants, together with members of their family and the injured, currently are going through agreed corridors in directions that they have chosen themselves voluntarily, including toward Idlib."

Before his statement, a truce was reached between Russia and Syrian rebels, opposition sources told ABC News, but the terms of the agreement were unclear.

The U.N. called for immediate access to the eastern neighborhoods of Aleppo to confirm that fighting has stopped and to oversee evacuation of civilians as well as withdrawal of rebels. The U.N. envoy for Syria, Staffan de Mistura, told reporters that up to 50,000 civilians are still believed to be in eastern Aleppo and that they should be allowed to go with the rebels to Idlib, an opposition stronghold, if they want.

The Russian announcement came after months of siege and years of fighting between rebels and Syrian government forces. In recent months, the Syrian government, with help from its Russian and Iranian allies, intensified its airstrikes on eastern Aleppo and tightened the siege in an attempt to gain full control of the area, rebel held until recently.

By Tuesday morning, the Syrian government had taken over the city except for a small and shrinking enclave in the eastern part of the city. Gaining control of the eastern neighborhoods is a strategic victory for President Bashar al-Assad.

Earlier, the U.N. said that Syrian government forces reportedly entered civilians' homes and killed people inside "on the spot" in eastern Aleppo.

At least 82 civilians, including 11 women and 13 children, were reportedly killed in four eastern Aleppo neighborhoods — Bustan al-Qasr, al-Fardous, al-Kallaseh and al-Saleheen — U.N. spokesman Rupert Colville told reporters in Geneva.

"Civilians have paid a brutal price during this conflict, and we are filled with the deepest foreboding for those who remain in this last hellish corner of opposition-held eastern Aleppo," he said. "While some reportedly managed to flee yesterday, some were reportedly caught and killed on the spot, and others were arrested."

Multiple sources have reported that dozens of civilians were shot and killed Monday in al-Ahrar Square in al-Kallaseh and in Bustan al-Qasr by government forces and their allies, allegedly including al-Nujaba, an Iraqi armed group, Colville added.

Zeid Ra'ad al-Hussein, the U.N. high commissioner for human rights, warned that the bloodshed in Aleppo could spread to other rebel-held areas in Syria if the international community does not act.

"What can happen next, if the international community continues to collectively wring its hands, can be much more dangerous," he said. "What is happening with Aleppo could repeat itself in Douma, in Raqqa, in Idlib. We cannot let this continue."

U.N Secretary General Ban Ki-moon was "alarmed over reports of atrocities against a large number of civilians, including women and children, in Aleppo," his office said.

"I'm seeing people who are awaiting death. I'm seeing destruction," Abdulkarim Sergieh, a resident and media activist in the remaining rebel-held areas, told ABC News in a text message on Tuesday morning. "I'm seeing wounded who no one can help. I'm seeing a mother and father who are looking for food for their children and can't find any. I'm seeing people who are cold without anything to keep them warm."

Eastern Aleppo has been under siege for months, and its residents have not received U.N. aid since July. Thousands of civilians are believed to be trapped in neighborhoods that, until recently, were under opposition control — including activists and Syrian Civil Defense members who are "at risk of grave violations, including detention, torture and killing," according to the U.N.