The UN aid chief warned Thursday (September 29th) that Aleppo faces a humanitarian catastrophe "unlike any" witnessed so far in Syria's five-year war, AFP reported.

"Let me be clear: east Aleppo this minute is not at the edge of the precipice," Stephen O'Brien told the Security Council. "It is well into its terrible descent into the pitiless and merciless abyss of a humanitarian catastrophe unlike any we have witnessed in Syria."

The council was meeting to discuss the crisis in Syria as France said it would push for a UN resolution imposing a ceasefire in Aleppo, which has been under fierce bombardment for a week.

O'Brien appealed for action from the council after diplomatic efforts last week ended in failure, triggering a new upsurge in violence on the ground.

More than 100,000 children remain trapped in opposition-held east Aleppo, which has come under intense bombing since the Syrian regime announced on September 22nd an offensive to retake the city.

On Friday, regime forces advanced in northern and central Aleppo, backed by an air campaign.

Doctors Without Borders on Friday accused the regime and its allies of provoking a "bloodbath" in the city, saying the opposition-held area had become "a giant kill box".

Save the Children meanwhile said Friday that the use of bunker-busting bombs meant it would be too dangerous for children to return to school this weekend even to underground classrooms.

The "ferocious assault" on Aleppo could deprive almost 100,000 school-age children of an education, said the charity, which supports 13 schools in the city, eight of them underground.