Yarmouk, a Palestinian neighborhood in Damascus, has been under siege by the Syrian army since July 2013.
At least 55 have died from hunger and the majority of children are suffering from malnutrition, according to a Palestinian activist living in Yarmouk.
About 20,000 people are currently besieged. The regime of Bashar al-Assad says "terrorists" are holding people hostage in besieged areas. Syrian jets have also been bombing the area.
This picture, published by United Nations Relief Workers Agency, shows people waiting for food aid.
"I am deeply disturbed and shaken by what I observed today," UNRWA's Commissioner General Filippo Grandi said after he entered Yarmouk camp on Tuesday. "The Palestine refugees with whom I spoke were traumatized by what they have lived through, and many were in evident need of immediate support, particularly food and medical treatment."
Grandi said his experience "underlines the timeliness of the UN Security Council resolution 2139 on Humanitarian Access and the need for all sides to implement the resolution without fail."
The resolution was passed last week, but it has stalled.
"There are views that this resolution finally has some teeth. I don't see it that way," an aid worker in the region told Reuters.
A quarter of a million people are stuck in besieged areas around the capital. Reuters notes that the Syrian regime and to a lesser extent rebels fighting to overthrow him have been blocking food and medical care.