A United Nations official was reportedly shocked to witness the death of a severely malnourished 16-year old boy who died "in front of our eyes'' in the besieged Syrian town of Madaya near Damascus.

Hanaa Singer, UN children's agency representative in Syria, said in a statement Friday that the boy in the horrifying scene was identified as Ali, who died of starvation on Thursday in a clinic in the said town, the Los Angeles Times reported.

Singer said the boy was one of nearly 30 children trapped in the besieged town who showed signs of moderate to severe malnutrition during screenings this week at a makeshift clinic.

Two other communities besieged by Syrian rebels, the villages of Foua and Kfarya in northern Syria, were also included in the aid operation.

"The people we met in Madaya were exhausted and extremely frail," said Singer, of UNICEF. "Doctors were emotionally distressed and mentally drained ... It is simply unacceptable that this is happening in the 21st century."

Abeer Pamuk of SOS Children's Village in Syria, another aid worker who entered Madaya, said the situation inside is so dire as desperate parents resort to giving children sleeping pills in order to calm hunger. "Their parents had nothing to feed them. So they give them pills to let them sleep and forget about their hunger. None of the children I saw looked healthy.''

Doctors Without Borders later found that five people died of starvation after the first humanitarian aid convoy since October arrived in Madaya on Tuesday afternoon last week.

"Some of the current patients may not survive another day,'' said Brice de le Vingne, director for operations for the medical aid organisation MSF. "Medical evacuations for the most critically sick and malnourished need to happen immediately, and it is hard to understand why patients clinging to life have not already been evacuated.''

The group recorded 23 patients who died of starvation in Madaya in January; five died on Jan. 10, and two more died Tuesday as the first convoy was en route. With five new deaths, the total number of deaths from starvation confirmed by the MSF-supported medics in Madaya is 35, the report said.

Madaya, which is about 25 miles northwest of the Syrian capital, Damascus, has gained global attention in recent weeks after reports have surfaced of a looming humanitarian disaster in the opposition-held town that has been surrounded by pro-government forces for months.

Humanitarian agencies say that dozens of people have died there of starvation and a lack of medical care.

U.N. Secretary-General Ban Ki-moon meanwhile expressed concern at the scenes in Madaya, saying they represent "shocking depths of inhumanity.''

"Let me be clear: The use of starvation as a weapon of war is a war crime," Ban told reporters. "I would say they are being held hostage, but it is even worse. Hostages get fed."

The U.N. Security Council has set an emergency meeting on Friday at the request of Western countries tying to press Syria's warring parties to lift sieges on towns where hundreds of thousands have been cut off from aid, according to reports.

He called on both the Syrian government and rebels to end the sieges before the commencement of peace talks scheduled for Jan. 25 in Geneva.