"We have received indications that attacks, including air strikes are continuing in areas controlled by the moderate opposition," Ayrault told reporters 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," he said on the sidelines of the UN Human Rights Council.
His comments came as a fragile ceasefire, negotiated by Washington and Moscow and backed by the UN, entered its third day largely intact despite reports of violations on both sides.
Ayrault insisted France "fervently wants an end to hostilities," adding that it "would be vigilant about its concrete application".
Also Read
"Let us not be mistaken: the Syrian drama 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."
The ceasefire, which does not apply to territory held by the Islamic State group and Al-Qaeda affiliate Al-Nusra Front, is considered the biggest diplomatic push yet to help end Syria's conflict, which has claimed more than 270,000 lives since March 2011.
France, he said, "will not be on the side of those who want to place human and humanitarian rights in parenthesis, (sweep them) under the carpet".