14/12/2016 9:38 AM AEDT | Updated 14/12/2016 1:50 PM AEDT

U.S. Ambassador Samantha Power Savages Assad, Russia Over Aleppo Atrocities

'Are you truly incapable of shame?'

The United Nations has described the four-year battle for Aleppo between rebel militia and Bashar al-Assad's Syrian Army as a "complete meltdown of humanity" and "carnage".

As a ceasefire was called overnight, ending the rebel resistance in the Syrian city after years of bloodshed, the United States Ambassador to the UN Samantha Power launched a scathing salvo at an emergency meeting of the Security Council.

Pointing the finger squarely at Syria, Russia and Iran -- three member nations of the UN -- Power pointedly asked whether the parties were "incapable of shame" and blamed them for "tightening the noose" around thousands of innocent, displaced and murdered civilians.

"Three member states of the UN contributing to a noose around civilians. It should shame you. Instead, by all appearances, it is emboldening you," Power said.

"You are plotting your next assault. Are you truly incapable of shame?"

The battle of Aleppo, one of the worst of a civil war that has drawn in global and regional powers, ended with victory for al-Assad and his military coalition of Russia, Iran and regional Shi'ite militias.

For rebels, their expected departure with light weapons starting on Wednesday morning for opposition-held regions west of the city is a crushing blow to their hopes of ousting Assad after revolting against him during the 2011 Arab uprisings.

Power, clearly exasperated, continued by asking a series of questions of the al-Assad coalition.

"Is there literally nothing that can shame you?" she said.

"Is there no act of barbarism against civilians, no execution of a child, that gets under your skin? That just creeps you out a little bit? Is there nothing you will not lie about, or justify?"

Russia's UN envoy Vitaly Churkin didn't take kindly to Power's statement, accusing her of masquerading as "Mother Theresa" and asking: "What country is she representing?"

The plight of civilians has caused global outrage in the wake of a sudden series of advances by the Syrian army and its allies across the rebel enclave over the past two weeks.

"We appear to be witnessing nothing less than ... a total uncompromising military victory," U.N. Secretary-General Ban ki-Moon told the U.N. Security Council on Tuesday, who earlier urged they must do everything in their power to "stop the carnage".

-with Reuters