Paris is "very concerned" by the renewal of fighting and called for an end to the regime's bombardment in the Idlib region, close to the Turkish border, and the East Ghouta area near Damascus, Parly told France Inter radio.
The attacks are "unacceptable on account of their severity and their consequence for the population", the minister said, adding that France had several times demanded that they stop.
"We are also calling for humanitarian corridors to be opened because civilian populations are being targeted," she said.
The US alleges that at least six chlorine gas attacks have been recorded in rebel-held areas since the beginning of the year and France has said it believes such attacks are taking place.
The Syrian government denied using chemical weapons at the end of January and its Russian allies denounced a "propaganda campaign", stressing that "the authors have not been identified".
Last May French President Emmanuel Macron told Russian leader Vladimir Putin that the use of chemical weapons in Syria was a "red line" that would be met with an "immediate response" by France.
Parly said that stage had not been reached yet because "in the absence of certainty about what happened, about the consequences of what happened".
"We have indications of the possible use of chorine has but we do not have absolute confirmation," she said. "So we're carrying out this work of confirmation, with other people, because obviously the facts have to be established."
Asked about the Turkish offensive against the Kurdish People's Protection Units (YPG), who were backed by the US-led coalition in the fight against IS, Parly said France's only objective in Syria was to "finish the fight with Daesh [IS]".
"So everything that disrupts or diverts anyone from that objective must be excluded, proscribed".
In a telephone call later, Macron called on Putin to do "everything possible" to stop the degradation of the situation in East Ghouta and Idlib.