Hundreds of elite regime troops moved into east Aleppo on Thursday (December 1st), after the UN warned the city risked becoming a "giant graveyard", AFP reported.

After overrunning the city's north-east, regime forces are in control of 40% of the territory once held by opposition forces in Aleppo, the Syrian Observatory for Human Rights said.

"The regime is tightening the noose on the remaining section of east Aleppo under opposition control," Observatory head Rami Abdel Rahman said.

Hundreds of fighters from the Syrian Republican Guard and 4th Division arrived in Aleppo on Thursday "in preparation for street battles" in the densely populated south-east, he said.

"They are moving in on the ground, but they are afraid of ambushes because of the density of both residents and fighters," he said.

The latest civilian toll now stands at more than 300 civilians, including 42 children, since the offensive began on November 15th.

Thousands have sought refuge in the remaining opposition-held neighbourhoods in south-eastern Aleppo, while another 50,000 have poured out into territory controlled by regime forces or local Kurdish authorities, the Observatory said.

UN envoy Stephen O'Brien on Wednesday called on the UN Security Council to help break the Aleppo siege, calling on "those with influence to do everything in their power to protect civilians and enable access to the besieged part of eastern Aleppo before it becomes one giant graveyard".

Residents have been scavenging for food, hospitals are not functioning after repeated military strikes and an estimated 25,000 people have taken dangerous escape routes out of eastern Aleppo since Saturday alone, O'Brien said.

The opposition National Coalition on Wednesday urged the Security Council in a letter to "take immediate, definitive steps to protect civilians in Aleppo and stop the barbaric offensive against them".