"France demands United Nations observers to guarantee that the evacuation of civilians are a priority but also so that the combatants are not massacred," Foreign Affairs Minister Jean-Marc Ayrault said on France 2 TV on Wednesday.
The evacuation, which was supposed to start at dawn according to rebel groups, Russia and Turkey, did not start as promised and Ankara accused government forces of preventing it taking place.
Russia's defence ministry said that the Syrian army had resumed its assault after rebels broke the truce intended to allow them to evacuate.
"Humanitarian organisations such as the Red Cross and Unicef must also be able to intervene," Ayrault added, saying there was "total confusion".
At a UN Security Council meeting on Tuesday evening US ambassador Samantha Power claimed that civilians fear "they will be shot in the street or carted off to one of Assad's gulags".
On Tuesday Ayrault said there were reports of "cold-blooded killings of entire families", "summary executions, including of women and children" and "people burned alive in their homes".
"Such atrocities are unconscionable. Supporters of the regime, starting with Russia, cannot let this happen," he said.