DAMASCUS, Syria — Palestinian groups agreed to join forces with the Syrian government to expel Islamic State militants from an embattled Palestinian refugee camp in Damascus, opening the door to a potentially destructive military campaign in a district already devastated by many rounds of fighting.
But the head of the U.N. cautioned that a military assault on the Yarmouk camp would be "yet one more outrageous war crime for which those responsible must be held accountable."
Islamic State extremists overran much of Yarmouk last week, establishing a foothold in the Syrian capital for the first time. The incursion is the latest trial for Yarmouk's estimated 18,000 remaining residents, who have already suffered through a devastating, two-year government siege, starvation and disease.
Reporters on a government-escorted visit Thursday to Yarmouk saw blown-out buildings at the camp's northern entrance that were nothing but empty shells. In its dusty and deserted streets, a few sheep foraged in the rubble. Building facades were charred by fire and walls were pockmarked by bullets.
"There has been an agreement with the Syrian side to expel IS from Yarmouk as part of a joint Syrian-Palestinian effort," said Ahmad Majdalani, a Palestinian Authority envoy who was sent to Damascus this week.
"We will establish a joint military operation between the Syrian army and Palestinian factions, and this (operations) room will lead the military campaign to oust IS. The campaign will start soon."
His comments echoed those of a Syrian government official who said Wednesday that pushing back the IS extremists from the camp by force was a "top priority" and the only option. That also suggested that a wide-scale military operation was imminent.
The latest fighting in Yarmouk has worsened an already desperate situation for civilians trapped in the besieged camp. Residents say there is barely enough food and water, and hospitals have long run out of drugs and supplies.
The International Committee of the Red Cross joined a growing number of groups calling for immediate access for humanitarian aid to Yarmouk.
U.N. Secretary-General Ban Ki-moon said the mayhem has turned Yarmouk into "the deepest circle of hell."
"A refugee camp is beginning to resemble a death camp," Ban told reporters at the U.N., adding that the residents, including 3,500 children, are being turned into human shields by armed elements inside Yarmouk and government forces outside it.
Syrian opposition figures have suggested that President Bashar Assad may have facilitated the entry to Yarmouk by militants of the self-proclaimed Islamic State as an excuse to hit back hard at the rebels in the camp. The fighters surged from the southern district of Hajar Aswad last week, overrunning the camp in few hours.
The militant advance is also a source of concern for Assad, who has invested heavily in trying to secure his grip on Damascus and subdue the ribbon of rebellious suburbs surrounding the capital.
Majdalani told The Associated Press by telephone that all the Palestinian factions in Yarmouk agreed to take part in the joint military operation command with the Syrian army that will spearhead the campaign against the Islamic State in the camp, including anti-Assad Palestinian groups.
The most notable is Aknaf Beit al-Maqdis, a Hamas-affiliated group that has been the main force fighting IS militants in Yarmouk. Majdalani said the Syrian government agreed to pardon Aknaf Beit al-Maqdis leader Mohammad Zaghmout, who was recently wounded and allowed treatment outside the camp at a government hospital.
There was no immediate comment from Palestinian groups in Yarmouk, and it was not clear whether the official's position was shared by the fighters on the ground. Sporadic fighting continued Thursday, although on a smaller scale than before.
Majdalani said the Palestinians insist the operation preserve civilian lives, their property and the general infrastructure of the camp.
Ban said a massive assault on the camp "would be yet one more outrageous war crime for which those responsible must be held accountable."
"Civilians must be spared. Civilians must be protected at all times," he said. "We simply cannot stand by and watch a massacre unfold."
Yarmouk was the main camp established in Syria for Palestinians who fled the 1948 war that attended Israel's creation. Before the Syrian civil war, it was a sprawling, built-up neighborhood that was home to tens of thousands of Palestinians and Syrians. Only 10 percent of the camp's inhabitants remain.
Once the Syrian conflict began in March 2011, some Palestinian factions based in the camp, including Hamas, sided with Sunni rebels fighting to topple the government, and it became a refuge for anti-Assad activities. The government imposed a suffocating blockade, preventing the entry of basic supplies for two years — except for sporadic U.N food parcels. The U.N. says about 200 people have died in that time from hunger-related illnesses.
The devastation from four years of conflict was plain to see Thursday.
Battered water tanks stood in the streets, used as barriers by fighters. Downed electrical cables and rubble covered the pavement, and the top floors of some buildings had collapsed. An aid distribution center once run by the U.N. agency for Palestinians, known as UNRWA, was destroyed by shelling.
The ICRC said emergency medical care is "urgently needed" for those still in Yarmouk, and warned that humanitarian needs "are growing by the day." It urged armed factions to allow the "immediate and unimpeded passage" of humanitarian aid and to permit civilians who wish to flee to do so.
David Miliband, president of the International Rescue Committee, said the world was shocked last year by photos of Yarmouk residents lining up for food, and the IS takeover has proved to be "another shock."
"There are really profound concerns about the living conditions in the camp, and for that to be exacerbated now by a security fight is obviously very real," the former British foreign secretary told the AP in an interview in Beirut.
Daraghmeh reported from Ramallah, West Bank. Associated Press writers Ryan Lucas, Zeina Karam and Bassem Mroue in Beirut, and Cara Anna at the United Nations contributed to this report.