Food rations are running out fast in rebel Aleppo

The last of the food rations in eastern Aleppo are being distributed as war-torn Syria braces for its worst winter yet.

Fears of mass hunger as temperatures plummet have reawakened calls for UN humanitarian aid to be allowed access to the contested city.

"The fifth war winter is starting in Syria. There is no doubt it will be the worst in this cruel war, and I fear it will be a real killer in too many places," said Jan Egeland, Special Advisor to the UN Special Envoy for Syria.

"Some of the areas are freezing cold, horrible conditions, and people will be in need of digging themselves down in the ground in extreme cases," he said.

Aid convoys are only allowed in with President Bashar al-Assad's blessing or face being blocked by security forces at checkpoints. Safety fears have also prevented aid workers from entering hard to reach areas despite promises of pauses in fighting.

Egeland said the last time eastern Aleppo, where 275,000 people are thought to be trapped, had received supplies was at the beginning of July.

"There will not be more to distribute next week," he said, as the Russian-backed regime launches a fresh bombing campaign on the rebel-held districts.

I have not seen a place where there has been so much politicisation, manipulation of aid, as we have seen in Syria in recent months. It has to stop

The UN has put forward a humanitarian initiative to the negotiating parties including Russia, the Syrian government and armed opposition groups.

It calls for four actions to save the besieged population in eastern Aleppo: distribution of medical supplies to the medical facilities; medical evacuations for the estimated 300 or so patients, together with their families; delivery of food and other urgent humanitarian relief supplies; and dispatch of more personnel to provide medical relief.

"None of the four elements are conditional on the others," Egeland said.

"Having heard back from the [humanitarian] taskforce today, we are hopeful that both sides will, since the situation is so horrendous as it is, grant us the opportunity to both come with supplies into east Aleppo, and evacuate wounded and others out of east Aleppo," he said.

The International Syria Support Group (ISSG) has established the respective taskforces on humanitarian aid delivery and a wider ceasefire. Russia and the United States are the co-chairs of the taskforces and the ISSG, which also comprises the UN, the Arab League, the European Union and 16 other countries.

"I do not think anybody wants a quarter of a million people to be starving in east Aleppo," he said. "I do believe we will be able to avert mass hunger this winter."

There are also hardships in western Aleppo, which can still be reached with aid, he said, warning that civilians there are dying every single week from the continued fighting.

Egeland added the situation in besieged towns of Madaya, Zabadani, Foah and Kafraya, with relief and medical evacuations paralysed because of the "conditioning" between Iran and Ahrar al-Sham.

"I have not seen a place where there has been so much politicisation, manipulation of aid, as we have seen in Syria in recent months. It has to stop," he said.

The US last month accused the Syrian regime of using "starvation as a weapon of war" - a war crime under the Geneva Conventions.