"We have received indications that attacks, including air strikes are continuing in areas controlled by the moderate opposition," Ayrault said on the sidelines of the UN Human Rights Council in Geneva. "This must all, of course, be verified. France has therefore asked that the task force overseeing the implementation of the cessation of hostilities meets without delay."
As the UN tried to deliver aid to thousands of besieged civilians, the task force, co-chaired by Moscow and Washington, was to meet on Monday at 1400 GMT to evaluate allegations of breaches, a Western diplomat said.
At the weekend Russia, which backs President Bashar al-Assad's government, traded accusations with the main opposition grouping, the High Negotiations Committee, over truce violations.
"As of now I can tell you that by and large the cessation of hostilities is holding even though we have experienced some incidents," UN chief Ban Ki-moon said in Geneva.
France "fervently wants an end to hostilities," Ayrault said, adding that it "would be vigilant about its concrete application".
"Let us make no mistake: the Syrian tragedy is the measure with which all our efforts in the realm of human rights will be judged," he said. "For now we must observe that we have failed."
He called on the UN Security Council to take those guilty of violations to the International Criminal Court in the Hague.