The United Nations said today civilians faced starvation and dehydration in a Palestinian refugee camp on the outskirts of Damascus, where Islamic State is battling other Islamist groups for control.

U.N. Relief and Works Agency for Palestine Refugees (UNRWA) which aids Palestinian refugees across the region said it estimated up to 10,000 civilians were trapped in their homes in Yarmouk, which is on the southern outskirts of Damascus.

"Whatever supplies of food and water they had have long been exhausted. Given the frequently intense fighting, the overwhelming risk of serious injury and death prevents civilians from leaving their homes to search for food, fetch water, or seek medical treatment for injuries," UNRWA said in a statement.

"Credible reports from inside Yarmouk indicate extensive, deliberate fire-damage to homes and other civilian buildings on a scale hardly seen before. The precarious security situation also prevents UNRWA from continuing its humanitarian missions to the adjacent area of Yalda," it said.

The Syrian Observatory for Human Rights, a Britain-based organisation that reports on the war, says most of Yarmouk camp is now under the control of Islamic State.

UNRWA said: "The fighting has been intense, and is taking place in the most densely populated areas of Yarmouk, with the use of heavy weapons, explosive devices and weapons of indiscriminate effect."