Video report by ITV News Correspondent Dan Rivers
The battle for Aleppo between Syrian government troops and rebel forces that has raged for more than four years could be over "within hours".
Rebel fighters fled from most of their final strongholds on Monday following a three-week government advance into the war-torn city, according to the Syrian Observatory for Human Rights.
ITV News Correspondent Dan Rivers, who is in Syria, said: "Defeat seems inevitable for the rebels here. The only question is whether it comes in hours or days".
However, there is growing concern for the tens of thousands of people who are believed to be trapped in a rebel-controlled neighbourhood of Aleppo as the Syrian Army continues its offensive.
UN General Secretary Ban Ki-Moon said he is alarmed at unverified reports of atrocities against large numbers of civilians there.
A spokesman said he is conveying grave concerns to the relevant parties.
Hundreds of thousands of civilians had found themselves besieged in the eastern-held, rebel half of the city in recent months, as government forces attempted to push out the insurgents.
The Syrian Army have already claimed victory, but ITV News has spoken to one resident, Salah Al-Ashkar, who claims "we are still here, under siege".
He said: "There are a lot of children and people [who are] helpless.
"There is no possibility of resistance. The only way out is an international ceasefire and evacuation. That's the only solution, otherwise everyone will either be detained or killed."
In recent weeks, Russian-backed Syrian forces had continued their intense advance to regain full control of Aleppo, one of Syria's largest cities.
Approximately 20,000 people were estimated to have left rebel-held areas on Saturday alone.
For over a year, civilians in eastern parts of Aleppo have been subject to almost constant bombardment.
In the past four years, more than 20,000 residents of Aleppo province have been killed, according to the Syrian Observatory.
More than 80% of these are estimated to have been in rebel-held areas.
Almost all of Aleppo's hospitals have been bombed out of action, while basic foods and supplies continue to remain dangerously low.
Meanwhile, an emergency debate on what the UK can do to help rescue civilians in Aleppo will be held on Tuesday.
Conservative Andrew Mitchell successfully petitioned Commons speaker John Bercow to allow MPs to discuss how best the UK can use its "immense diplomatic muscle" to help secure a ceasefire.
He said: The debate would enable us to explore [ways the UK] can do more to secure a deal that will ensure a ceasefire for at least 24 hours to enable innocent civilians to be rescued from the hideous circumstances which now prevail in east Aleppo."
Mitchell cited reports that sarin and chlorine gas have been used in the city, which would constitute a war crime, as evidence for immediate action.