The civilian toll is the result of both parties' conduct. From the UN report released on September 11:
Government and pro-government forces have continued to conduct widespread attacks on the civilian population, committing murder, torture, rape and enforced disappearance as crimes against humanity. They have laid siege to neighbourhoods and subjected them to indiscriminate shelling. Government forces have committed gross violations of human rights and the war crimes of torture, hostage-taking, murder, execution without due process, rape, attacking protected objects and pillage.
Anti-government armed groups have committed war crimes, including murder, execution without due process, torture, hostage-taking and attacking protected objects. They have besieged and indiscriminately shelled civilian neighbourhoods.
Anti-government and Kurdish armed groups have recruited and used child soldiers in hostilities.
The perpetrators of these violations and crimes, on all sides, act in defiance of international law.