GENEVA — Hundreds of Syrian men escaping rebel-held areas of Aleppo to go to government-controlled parts of the city are missing, and there were reports of government reprisals, including numerous arrests and several cases of summary killings of people perceived to be opposition supporters, United Nations rights officials said on Friday.
At the same time, the officials said, rebels have in some cases prevented civilians from leaving, and there are reports that some groups killed or kidnapped residents who had demanded that insurgents leave their neighborhoods.
The United Nations reports largely track what residents of eastern Aleppo have told The New York Times. Several have described how family members were detained, arrested or conscripted after crossing to government-held areas, and one resident recounted how rebels in the Bustan al-Qasr area had stopped civilians from leaving on two recent occasions.
Other residents, however, said that rebels had helped them cross the front lines, or warned them not to go at certain times because of danger before allowing them to leave. Rebel groups inside eastern Aleppo are fragmented and do not always act in concert.
Family members reported that they had lost contact with men ages 30 to 50 after they had fled from eastern Aleppo into government-held areas a week to 10 days ago, said Rupert Colville, a spokesman for the United Nations high commissioner for human rights, Zeid Ra’ad al-Hussein.
Amid the chaos in the city, investigators could not determine the fate of the missing men, Mr. Colville said, but they cited reports that forces loyal to President Bashar al-Assad of Syria were advancing from the north into eastern Aleppo, where they had carried out reprisals.
Exemplifying the dangers of bloody retaliation, two National Defense Force members who were among the pro-government forces that took over the al-Halk neighborhood of Aleppo on Sunday were reported to have shot four men in front of their families because of their purported sympathy for the opposition.
Other civilians have been detained, including the wife of a dead leader of the Free Syrian Army, an alliance of insurgents, Mr. Colville said. He also expressed deep concern for about 150 activists remaining in the increasingly small territory still controlled by opposition groups.
“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,” Mr. Colville said.
Two armed opposition groups, Jabhat Fateh al-Sham and the Abu Amara Battalion, had reportedly abducted and killed an unknown number of civilians who had asked the groups to leave their neighborhoods, Mr. Colville said. The opposition groups also demanded that activists identify people in the neighborhood who objected to their presence, he said.
Civilians attempting to leave the Bustan al-Qasr neighborhood between Nov. 30 and Dec. 1 reportedly came under fire from armed opposition groups, Mr. Colville said, adding that the actions of the fighters could amount to hostage taking, which is a war crime.
“Civilians are caught between warring parties that appear to be operating in flagrant violation of international humanitarian law,” Mr. Colville said. “All sides are deeply culpable.”