Alarming photos have hit the internet, showing armed French police officers surrounding a middle-aged Muslim woman on the beach and making her remove some of her clothing.
The incident took place on the Promenade des Anglais in Nice, following the recent introduction of a "burkini" ban.
Following recent terrorist attacks by Islamic extremists in France and under the guise of "secular freedom", some 15 French towns have passed bylaws banning the burkini, triggering a fierce debate about the wearing of the full-body swimsuit, women's rights and secularity.
But French police appear to be cracking down on any type of headscarf worn on the beach, including at the incident in Nice, among others.
"This type of row is totally counterproductive and plays into [terrorist group] ISIS's hands," says Feiza Ben Mohamed, secretary general of the Federation of Muslims of the South of France.
"It's exactly what ISIS want - the mayor is doing their work for them. ISIS seeks to make our young people believe that they are excluded, stigmatised, and they will use such examples in their recruitment drive."
Another Muslim woman was reportedly accosted by armed French police on the beach at Cannes and ordered to leave the area for wearing a headscarf.
The 34-year-old mother, who was with her children at the time, said she was threatened with pepper spray - a claim backed up by a France 4 TV journalist.
"My children were crying as they witnessed by humiliation," said the woman, identified only as "Siam".
"Today we are not allowed on the beach. Tomorrow, the street? Tomorrow, we'll be forbidden from practising our religion at all?
"I'm in the country of human rights. I see no trace of the principles of liberty, equality and fraternity. I am outraged that this could happen in France."
A lower court in Nice ruled on Monday (local time) that the burkini ban was "necessary, appropriate and proportionate" to prevent public disorder.
Clothing that covers much of a woman's body was "liable to offend the religious convictions or [religious] non-convictions of other users of the beach", and "be felt as a defiance or a provocation exacerbating tensions felt by" the community, it added.