The United Nations appealed on Monday for the Syrian army and rebel fighters to allow urgent aid to reach a Palestinian district of southern Damascus where it said 15 people have died of malnutrition in recent months.
UN Relief and Works Agency (UNRWA) spokesman Chris Gunness said five Palestinian refugees died in the Yarmouk district over the weekend. Ten others have died since September, the last time the UN was able to deliver aid to Yarmouk.
"The situation has progressively deteriorated for some 20,000 Palestinians trapped inside Yarmouk," he told Reuters.
"The continued presence of armed groups that entered the area at the end of 2012 and its closure by government forces have thwarted all our humanitarian efforts."
Syria is home to half a million Palestinians, refugees of the 1948 conflict which led to the creation of the state of Israel. Before the 2011 uprising against President Bashar Assad, many of them lived in the Yarmouk neighborhood on the southern edge of the Syrian capital.
But the 2011 protests led to a civil war which has driven out most Yarmouk residents, forcing them once again into homelessness. Those that remain in Yarmouk have been trapped by the fighting for months.
"If this situation is not addressed urgently, it may be too late to save the lives of thousands of people including children," Gunness said.
"We urgently ask all parties to immediately heed their legal obligations and facilitate the urgent provision of humanitarian assistance to Yarmouk and other Palestinian refugee camps where fighting impedes the delivery of such assistance."
A video uploaded by activists on Sunday showed people crowded around an UNRWA official, asking about aid deliveries.
"We just want this situation to end," one resident said. "We want the roads to be open for us, for people to come in and out safely ... We can't tolerate it any more."
Tens of thousands of Syrians are trapped in other besieged districts. In the Mouadamiya suburb southwest of Damascus, government forces and rebel fighters agreed a brief truce last week to allow food to be brought in.