Thousands of people fled the front lines of fighting in Aleppo on Tuesday as the Syrian regime and its allies advanced on the final pocket of opposition resistance.
The UN called the crisis in Aleppo a "complete meltdown of humanity." The UN said it had reports of abuses, including that the regime and allied militia had executed 82 civilians, including 11 women and 13 children, in captured districts.
"The reports we had are of people being shot in the street trying to flee and shot in their homes," said UN spokesman Rupert Colville. "There could be many more."
— United Nations (@UN) December 13, 2016
Colville described the rebel-held area as "a hellish corner" of less than a square kilometer, and said its capture was imminent.
"What is happening with Aleppo could repeat itself in Douma, in Raqqa, in Idlib. We cannot let this continue," said UN human rights chief Zeid Ra'ad al Hussein.
Syrian regime leader Bashar al Assad's forces now hold more than 90 percent of the one-time opposition stronghold of east Aleppo, and appear on the verge of retaking the entire city.
People trapped by the fighting say they want to escape, but Russia has blocked a US request for a ceasefire.
Turkey on Tuesday said it was "horrified and outraged" by the massacre reports. Turkish Foreign Minister Mevlut Cavusoglu said Turkey would meet with Russia on Wednesday and that a ceasefire was needed to allow civilians to evacuate.