“We were living on tree leaves, on plants,” said Majed Ali, 28, an opposition activist who spoke to Reuters by phone from Madaya. “But now we are struggling in a snowstorm, and there are no more plants or leaves.”

Ali said he lost close to 30 percent of his weight since the siege began, dropping from about 250 pounds to 176.

The Britain-based Syrian Observatory for Human Rights on Wednesday said at least 23 people, including children, have died in Madaya because of the siege, and at least 300 children are suffering from malnutrition.

Pawel Krzysiek, a spokesman for the Red Cross in Damascus, also outlined the scale of suffering in the area.

“We have seen credible reports that people are starving … People are hungry, and it is very cold out there with no electricity or fuel,” Krzysiek told the DPA news agency.

Medical professionals in Madaya said people “were eating grass to stay alive.”

“We cannot provide milk for infants,” Dr. Khaled Mohammed told DPA this week. “Today a 10-year-old child died of malnutrition.”

Melissa Fleming, chief spokeswoman for the U.N. refugee agency, told Al Jazeera that hundreds of thousands of people are in similar situations across Syria.

“We believe there are 400,000 people in 15 towns and cities who are in a situation where they are besieged by different parties to the conflict,” Fleming said.

“‘Besieged’ translates into civilians completely cut off from any humanitarian aid: no food, no medicine, shelters without heat and water. These are situations under which people cannot survive any more,” she said.