The World Food Programme says 8.7 million people are in urgent need of help
Food supplies in the besieged Syrian city of Aleppo are predicted to run out in just a few weeks.
The warning follows yesterday's shooting down of a helicopter, which had been delivering aid to the area.
The helicopter was manned by a Russian crew who were all killed when it was targeted on its way back to base.
A renewed siege of the city by government forces against rebels has left up to 300,000 people trapped in the city.
Supply routes into the city have been cut off with all aid now dependent on 'safe corridors' opened by the Syrian government.
The World Food Programme says 8.7 million people - 37% of the pre-conflict population - are in urgent need of help in the country.
"A staggering 89% of all Syrian refugees currently in Lebanon require urgent food, nutrition and livelihoods assistance," the WFP says.
Foreign affairs correspondent with Channel 4, Jonathan Rugman, says residents in Aleppo are trapped.
"(The United Nations) tried a few months ago to take aid in, they've given up on that," he told Newstalk Breakfast earlier.
"Everything the UN does rather depends on a ceasefire being brokered by the Russians and the Americans."
"There was a ceasefire a few months ago, but it didn't last - so the situation in Aleppo is that the food supplies are estimated to be running out in something like two weeks' time."