The Syrian Observatory for Human Rights, a British-based war monitor, said a suspected chemical attack by Syrian government or Russian jets killed at least 58 people, including 11 children, in the rebel-held northwestern province of Idlib.
"A new and particularly serious chemical attack took place this morning in Idlib province. The first information suggests a large number of victims, including children. I condemn this disgusting act," Jean-Marc Ayrault said in a statement.
"In the face of such serious actions that threaten international security, I ask for everyone not to shirk their responsibilities. With this in mind, I ask for an emergency meeting of the UN Security Council," he added.
It was not immediately clear what action France, a permanent member of the Security Council, wanted to be taken.
France, Britain and the United States in February put forward a resolution to impose sanctions targeting Syrian government officials over accusations of chemical weapon attacks during the six-year conflict.
Russia, backed by China, cast its seventh veto to protect the Syrian authorities and Russian President Vladimir Putin described the draft resolution as "totally inappropriate."
Western powers put forward the resolution in response to the results of an investigation by the UN and the Organisation for the Prohibition of Chemical Weapons (OPCW).
The international inquiry found Syrian government forces were responsible for three chlorine gas attacks and that ISIS militants had used mustard gas.
"The use of chemical weapons constitutes an unacceptable violation of the convention against chemical weapons and is another example of the barbarity that the Syrian people have been under for so many years," Ayrault said.
Before a meeting in Brussels on Wednesday to discuss aid for Syria, Ayrault said Europe could not play a role in the country's reconstruction without a credible transition.
(Reporting by John Irish, Editing by Sudip Kar-Gupta and Adrian Croft)