Nice has become the latest French seaside resort to ban the burkini, the body-concealing swimsuit associated with Islamic values that has sparked heated debate in France, city officials said on Friday.

Using language similar to bans imposed in a string of other towns on the French Riviera, the city barred apparel that "overtly manifests adherence to a religion at a time when France and places of worship are the target of terrorist attacks".

The wording of the ban in Nice refers specifically to last month's Bastille Day truck attack in the city that claimed 86 lives as well as the murder of a Catholic priest near the northern city of Rouen 12 days later.

Fifteen towns in the southeast, as well as others elsewhere in France, have already banned the burkini, including nearby film festival host city Cannes, where three Muslim women were each fined 38 euros ($43) under the new rule at the weekend.

Nice's deputy mayor Christian Estrosi, from the centre-right Republicans party, wrote in a letter to Prime Minister Manuel Valls on Tuesday that "hiding the face or wearing a full-body costume to go to the beach is not in keeping with our ideal of social relations".

Valls came under fire after saying on Wednesday that the burkini was "not compatible with the values of France and the Republic".

The Socialist premier cited the tensions in France after the militant attacks to justify his support for the mayors who barred a garment that he said was "founded on the subjugation of women".

Muslim advocacy and rights groups have criticised the ban.

Marwan Muhammad, a spokesman for the Collective against Islamophobia in France, said the bans restricted fundamental liberties and discriminated against Muslim women.

"This summer we are witnessing a hysterical political Islamophobia that pits citizens against one another," he said.

France's Human Rights League accused Valls of "participating in the stigmatisation of a category of French people who have become suspect by virtue of their faith".

Opponents of the ban accused French municipalities that imposed it of sexism. A photo of a woman in a burkini next to a man in a full-body wet suit circulated on the internet. Social media users pointed to the double standards of allowing men to cover their heads and bodies on the beach but not women.

The New York Times editorial board also slammed the bans, describing the measures as "hysteria".

"The fact that French parents are increasingly dressing their toddlers in remarkably similar suits to protect them from the sun, or that a wet suit also covers the head and body, adds to the hypocrisy of this debate," the Times editorial board wrote.

Burkinis are a rare sight on French beaches, where a small minority of Muslim women can be seen bathing in ordinary clothes and wearing headscarves.

Islamic dress has long been a subject of debate in France, which was the first European country to ban the Islamic face veil in public in 2010, six years after outlawing the headscarf and other conspicuous religious symbols in state schools.

Meanwhile, the imam of Florence, Italy, triggered a storm on Friday by posting on his Facebook page a picture of a group of eight nuns, veiled and dressed in their habits, on a beach.

Izzedin Elzir, who is also president of the Union of Islamic Communities of Italy, posted the picture without a caption but unwittingly sparked a wave of criticism.

The image was shared more than 2,000 times and drew many negative comments. Facebook blocked Elzir's profile page for several hours after receiving hostile notifications from users.

Interviewed on Sky Tg24 television, Elzir said he had simply sought to stir a "positive debate" and in fact had received messages from "very many Christians" to thank him.

He said he posted the picture "to respond to those who say that... Western values are different in the way people dress and cover their body".

"I meant that part of Western values comes from Christianity... and you can see that Christian roots are also derived from people who cover themselves almost completely."

Interior Minister Angelino Alfano said on Tuesday that Italy would not ban the burkini, saying the measure would be fruitless and even counter-productive, as it could cause a potential backlash.