A source said the toll figured in a document given by Prime Minister Jean-Marc Ayrault to lawmakers during a meeting on the Syrian crisis, adding that the attack was "massive."
The figure was markedly lower than that provided by Washington, which spoke of at least 1,400 deaths. The United States is trying to cobble together a coalition to launch strikes on Syria.
Assad's government has denied responsibility, blaming it on opposition fighters who it says are armed by the West.