French Foreign Minister Laurent Fabius on Monday said there were "mounting suspicions" that chemical weapons were being used in Syria.
Speaking to journalists after talks with his EU counterparts, Fabius said that "very detailed verification" was necessary however.
There were indications of "localised use" of chemical arms, he said.
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"We are consulting with our partners to examine what concrete consequences to draw," added Fabius.
He was then heading for Paris where he will meet his Russian and US counterparts Sergei Lavrov and John Kerry for talks on convening a Syria peace conference next month.
French newspaper Le Monde reported Monday that the Syrian army was using chemical weapons against rebel forces in the outskirts of Damascus.
It quoted two of its journalists who were in the area in April and May as saying they had "witnessed over several consecutive days" the use of explosive chemical weapons and their effects on rebel fighters in the village of Jobar on the outskirts of the capital.
Reporter Jean-Philippe Remy and photographer Laurent Van der Stockt reported that on April 13 they saw fighters "suffocating and vomiting" in the area after an apparent attack using chemical weapons.