A U.N. agency says around 10,000 civilians are trapped in "desperate" humanitarian conditions in a Palestinian refugee camp in Damascus, where fighting has raged for days between Islamic State militants and other extremists.

The U.N. Palestinian refugee agency, UNRWA, says residents of the Yarmouk camp have gone without food or water for more than a week.

UNRWA spokesman Chris Gunness says "civilians in Yarmouk are facing starvation and dehydration alongside the heightened risks of serious injury and death from the armed conflict."

The camp, a built-up neighborhood once home to an estimated 150,000 people, has been ravaged by fighting between the Islamic State group and al-Qaida's Syrian affiliate, the Nusra Front, while government forces regularly shell it from outside.