"Doomsday" for eastern Aleppo as reports of regime atrocities emerge

It's been a day of almost constant bombing raids, like Doomsday, as one resident described it.

People still inside east Aleppo have reported the killing of hundreds of civilians by advancing Syrian regime forces backed by Russia and Iran.

Regime and Iranian-backed Shia militias have started executing civilians in the neighbourhoods they have recently seized.

"The Shia militia gunmen immolated nine children and four women, and executed 67 men by firing squad in Firdaus and Kallasa districts today. These were all civilians," according to eyewitness Mahmud Sheikh, who spoke to Anadolu Agency.

Sheikh said, "There is no need to hide myself or identity anymore. We aren't afraid anymore. All of us will be killed anyway."

The volunteer-based non-governmental humanitarian organisation, Syria's Civil Defence or "The White Helmets" as they are commonly known, said they were trapped in a small area with tens of thousands of civilians, and were facing a horrific onslaught by advancing regime ground forces backed by Russian warplanes and Iranian-backed militia.

This was the last written statement by the White Helmets posted to Twitter before communication was cut off in eastern Aleppo:

With the recent attacks of Bashar Assad's regime and his Russian and Iranian support, the opposition had to withdraw from the Sheikh Saed, Firdaus, Hamdudu and Saliheen regions.

The area controlled by the resistance fell to 8.6 square kilometres, where about 100,000 civilians are under regime siege.

Bashar Assad's regime says the battle for Aleppo is in its final stages, but the rebel resistance claims it is not yet defeated as it takes its last stand to defend whatever they can in eastern Aleppo.

United Nations Secretary-General Ban Ki-moon is alarmed by unverified reports of atrocities against a large number of civilians, including women and children his spokesman said on Monday.

"The Secretary-General is conveying his grave concern to the relevant parties. He has instructed his Special Envoy for Syria to follow up urgently with the parties concerned," UN spokesman Stephane Dujarric said in a statement.

Here are some of the reactions coming in from social media site Twitter on the situation in eastern Aleppo:

Authors: Abed Ahmed and Emre Iren