Russian forces are believed to have used thermite, which burns at 2,200C, to bomb residential areas of Aleppo

Russia is breaching international conventions by dropping incendiaries similar to white phosphorus on to residential neighbourhoods in the Syrian city of Aleppo in what is thought to be the prelude to a ground assault to retake the city from rebel forces.

Photographs have also shown what experts believe to be a thermobaric bomb, the most powerful explosive apart from a nuclear weapon, being detonated next to urban areas, with potentially devastating effects for civilians.

Video footage has emerged showing the glowing showers of what is thought to be thermite raining down on a rebel-held suburb in the west of the city and starting huge fires.

A man carries a wounded girl after an airstrike on residential areas in the opposition controlled Tariq al-Bab neighbourhood of Aleppo BEHA EL HALEBI/ANADOLU AGENCY/GETTY IMAGES

Hussein Mohammad, the cameraman who shot the footage, said that six Russian aircraft started circling the city at about midnight