Some 400 people in the besieged Syrian town of Madaya need to be urgently evacuated for medical treatment, says UN humanitarian chief Stephen O’Brien.
Mr O’Brien was speaking after the UN Security Council held an urgent meeting to discuss the crisis in the rebel-held town near Damascus.
Earlier, an aid convoy brought food to 40,000 town residents who have been under government siege for months.
The UN says it has received credible reports of people dying of starvation.
Monday’s aid delivery was the first allowed into Madaya since mid-October, when the UN’s World Food Programme took a month’s supply of food rations for 20,000 people.
Simultaneously, aid lorries entered two towns besieged by rebel forces in the northern province of Idlib under a deal between the warring parties.
The situation in Foah and Kefraya is also said to be dire, with an estimated 20,000 people trapped there since March.
Mr O’Brien said that a humanitarian co-ordinator at the hospital in Madaya saw around 400 people who needed to be evacuated immediately.
“We must seek to do this and put the arrangements in place as soon as possible for medical treatment. Or they are in grave peril of losing their lives and dying with either the causes being from malnutrition or for complications for other medical reasons,” Mr O’Brien said.
A few town residents were given permission to leave and could be seen with their belongings awaiting evacuation.
In total, some 44 lorries operated by the UN, the International Committee of the Red Cross (ICRC), the Syrian Red Crescent and the World Food Programme (WFP) reached Madaya from Damascus on Monday.
The convoy brought in food and medicines, as well as blankets, shelter materials and soap, with distribution expected to continue through the night.
Pawel Krzysiek, who is with the ICRC in Madaya, said: “The people… were coming every five minutes asking, ‘Listen, did you bring food, did you bring medicine?’
“Some are smiling and waving at us but many are just simply too weak, with a very bleak expression, too tired.”