The US Ambassador to the United Nations has accused the Syrian regime, Russia and Iran of carrying out barbaric "crimes" in Aleppo.

Addressing an emergency meeting of the UN Security Council, Samantha Power said: "To the Assad regime, Russia and Iran, your forces and proxies are carrying out these crimes, your barrel bombs and mortars and air strikes have allowed the militia in Aleppo to encircle tens of thousands of civilians in your ever-tightening noose.

"It is your noose. Three member states of the UN contributing to a noose around civilians. It should shame you.

"Instead, by all appearances it is emboldening you. You are plotting your next assault."

Aleppo before the Syrian Civil War Show all 12 1 /12 Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man crosses a street in Aleppo, December 12, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A vendor sits inside an antique shop in al-Jdeideh neighbourhood, in the Old City of Aleppo, December 12, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A view shows part of Aleppo's historic citadel, overlooking Aleppo city, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A view shows part of Aleppo's historic citadel, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Visitors walk inside Aleppo's Umayyad mosque, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk inside the Khan al-Shounah market, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man walks past shops in al-Jdeideh neighbourhood, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk along an alley in al-Jdeideh neighbourhood, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Visitors tour Aleppo's historic citadel, Syria December 11, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A general view shows the Old City of Aleppo as seen from Aleppo's historic citadel, Syria December 11, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk near Aleppo's Bab al-Faraj Clock Tower, Syria October 6, 2010 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man stands inside Aleppo's historic citadel, overlooking Aleppo city, Syria December 11, 2009 Reuters

She added: "Are you truly incapable of shame? Is there literally nothing that can shame you?

"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? It there nothing you will not lie about, or justify?"

UN Secretary-General Ban Ki-moon told the emergency meeting he had received "credible reports" of civilians killed by pro-government forces as they swept into the last rebel areas in Aleppo.

The head of the UN's human rights office, Rupert Colville, had previously said that six different sources had confirmed 82 non-combatants were shot in four different neighbourhoods overnight on Monday.

A building with more than 100 children trapped inside was also allegedly attacked by pro-regime forces.

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Shelling resumed in the remaining rebel part of eastern Aleppo on Wednesday morning, despite a ceasefire deal intended to allow for the evacuation of rebel fighters and tens of thousands of civilians.

The Syrian army will resume its military opperations in the city, the Russian Defence Ministry said, blaming the rebels for infringing the fragile ceasefire.

Bashar al-Ja'afari, Syria's ambassador to the UN, denied any mass executions or revenge attacks, but said it was Syria's "constitutional right" to go after "terrorists," a reference to all opposition fighters.