Hundreds of Men Missing From Battered East Aleppo, UN Says They have reportedly been missing since they crossed into government areas.

 -- Hundreds of men appear to have gone missing after fleeing the rebel-held part of Aleppo, Syria, for government-held areas, the United Nations said on Friday, expressing concern that the men may have been detained and mistreated by the Syrian government.

“Given the terrible record of arbitrary detention, torture and enforced disappearances by the Syrian government, we are of course deeply concerned about the fate of these individuals,” Rupert Colville, spokesperson for the U.N. High Commissioner for Human Rights, said during a press briefing in Geneva.

The men who have reportedly gone missing are between the ages of 30 and 50, he said.

Syrian government forces loyal to President Bashar al-Assad, have captured approximately 85 percent of east Aleppo and are continuing to bombard areas that remain under the control of opposition forces, according to the Syrian Observatory for Human Rights.

Several activists in Syria have said that men leaving east Aleppo for government-held areas risk being detained, killed or recruited to join the Syrian army. The U.N. said that some of the civilians who have been trying to flee are reportedly being blocked by armed opposition groups.

In Friday’s statement, the U.N. voiced concern that approximately 500 people in east Aleppo are in need of urgent medical evacuation and that civilians in the area are caught between warring parties while the Syria Civil Defense, also known as the White Helmets, is barely operating.

"Civil Defense teams are still found within Aleppo and they are working now, but there is a big inability for the teams to respond to bombardments because of the intensity of the shelling and the destruction of equipment," Ibrahim Hilal, leader of the White Helmets in Aleppo, told ABC News, adding that the group's headquarters used to be in an area that has been seized by the government. "In addition, there are many people that the teams can't rescue because they are in areas that have fallen to the government."

On Wednesday night, nearly 150 civilians, most of them disabled or in urgent need of care, were evacuated from a hospital in the Old City of Aleppo. The hospital, Dar Al-Safaa, used to be a home for the elderly but it had lately been serving patients with mental health needs or physical disabilities. About three dozen civilians, a number of them injured, had also sought refuge there, said the Syrian Arab Red Crescent and the International Committee of the Red Cross.

"These patients and civilians had been trapped in the area for days because of heavy clashes nearby and as the front line kept drawing closer," the Red Cross' head of delegation in Syria, Marianne Gasser, who is currently in Aleppo, said in a statement. "Many of them cannot move and need special attention and care. It must have been terrifying for them. Our partners from the Syrian Arab Red Crescent had been trying to reach and evacuate them since Tuesday."

Around 100,000 civilians may still be trapped in the shrinking amount of rebel-held areas in Aleppo, with little access to health care, food, water and fuel for heating, according to the U.N.