An investigation by Amnesty International has found that civilians are suffering “horrific levels of violence” in the battle for Aleppo.
The NGO said Syrian government forces are carrying often indiscriminate attacks in areas where rebels are operating, putting local residents in grave danger.
Western powers believe Syria may unleash its stockpile of chemical weapons in the conflict.
The US and UK have hinted they may intervene if that happens.
But their fears have been dismissed by Russia, a long-time ally of President Bashar Assad.
Russia’s deputy foreign minister, Gennady Gatilov, said Assad’s government had given very clear assurances that chemical arms would not be used.
Amid Moscow’s backing of the Syrian regime, the military continued its attacks on the Sunni Muslim town of Daraya.
Over the past two days, Syrian forces have pounded the area, leaving 25 people dead and more than 200 wounded, according to opposition sources.
Some locals have already begun burying the dead from those attacks.