( CNN ) Thousands of Palestinians are trapped in the devastated Yarmouk refugee camp in Syria , which has mostly been seized by groups including ISIS , activists report . The London-based Syrian Observatory for Human Rights says ISIS and the al Qaeda-affiliated Al-Nusra Front took control of 90 % of the camp in southern Damascus . Calling the lives of Yarmouk refugees `` profoundly threatened '' on Sunday , the United Nations Relief and Works Agency issued a statement urging humanitarian aid access . `` Never has the hour been more desperate in the Palestine refugee camp of Yarmouk , '' the statement said . The UNRWA estimates 18,000 civilians remain trapped in the camp that has been engulfed in fighting between the government and rebel forces since December 2012 . Syria 's state-run SANA news agency reports up to 2,000 people have fled in the past two days as food , water and medical supplies remain scarce . `` All people are trying to leave the camp , '' says Syrian activist Abu Mohammed in Damascus who used to live in Yarmouk . `` There is no electricity , '' says Mohammed . `` ISIS controls the hospital so injured people have nowhere to go . '' The Syrian Observatory for Human Rights reports barrel bombs were dropped on the camp Sunday as clashes continued . The Palestine Liberation Organization called on international bodies to assist in the evacuation of people from the camp . `` Reports of kidnappings , beheadings and mass killings are coming out from Al- Yarmouk , which is under a brutal campaign of murder and occupation , '' Palestine Liberation Organization Executive Committee Member Dr. Saeb Erekat said Saturday . Yarmouk , the largest Palestinian refugee camp in Syria , was formed in 1957 to accommodate people fleeing the Arab-Israeli conflict . `` The levels of humanity that we have seen have now descended into further levels of inhumanity , '' said Chris Gunness , spokesman for the UNRWA . Yarmouk , he added , `` was always a place where human rights meant very little . We are seeing it descend further . '' CNN 's Samira Said contributed to this report .
ISIS and other rebel groups control most of the refugee camp , activists say . `` Never has the hour been more desperate '' in the camp , U.N. says . `` `` Reports of kidnappings , beheadings and mass killings , '' PLO official says .