The UN human rights office has condemned local bans in France on burkini swimwear as "a grave and illegal breach of fundamental freedoms" and a "stupid reaction" to recent extremist attacks.
Rupert Colville, spokesman for the Office of the High Commissioner for Human Rights, called on local officials to immediately lift the bans, saying they do not increase security.
It came after a French high court last week struck down a Mediterranean beach resort's ban on the burkini, effectively invalidating such orders in about 30 towns, although many remain in place.
Mr Colville said the bans "fuel religious intolerance and the stigmatisation of Muslims", and "have only succeeded in increasing tensions".
He said people who wear burkinis - body-covering beachwear worn by some Muslim women - or any other clothing "cannot be blamed for the violent or hostile reactions of others".
Friday's court ruling by the Council of State specifically concerned a ban in the Riviera town of Villeneuve-Loubet.
The bans grew increasingly controversial as images circulated online of some Muslim women being ordered to remove body-concealing garments on French Riviera beaches.
This woman was at a beach in France when the police came & forced her to remove her burkini.
No difference than ISIS pic.twitter.com/LuPHfbYSZd— Yasmine (@yasminebllt) August 24, 2016
Lawyers for a human rights group and a Muslim collective challenged the legality of the ban at the top court, saying the orders infringe basic freedoms and that mayors have overstepped their powers by telling women what to wear on beaches.
Mayors had cited multiple reasons for the bans, including security after a string of Islamic extremist attacks, risk to public order, and France's strict rules on secularism in public life.
The Council of State ruled: "The emotion and concerns arising from the terrorist attacks, notably the one perpetrated in Nice on July 14, cannot suffice to justify in law the contested prohibition measure."
It ruled that the mayor of Villeneuve-Loubet overstepped his powers by enacting measures not justified by "proven risks of disruptions to public order nor, moreover, on reasons of hygiene or decency".
"The contested decree has thus brought a serious and manifestly illegal infringement on basic freedoms such as freedom to come and go, freedom of conscience and personal freedom," the ruling read.
Lawyer Patrice Spinosi, representing the Human Rights League, said women who had already received fines could appeal against them based on the decision.
He said the group planned to ask all French mayors who banned burkinis to withdraw their orders and, if they refused to do so, he would systematically take each case to court.
"It is a decision that is meant to set legal precedent," Mr Spinosi said.
Many officials - including prime minister Manuel Valls - have argued that burkinis oppress women, but two ministers of Mr Valls's cabinet - education minister Najat Vallaud-Belkacem and health minister Marisol Touraine - have said banning burkinis is not a good option.
Ms Vallaud-Belkacem, a feminist with North African roots, argued that while she does not like the burkini, banning the garment amounted to a politically driven act that encouraged racism.
The conservative mayor of Villeneuve-Loubet, Lionnel Luca, said that "far from calming, this decision can only heighten passions and tensions, with the risk of trouble we wanted to avoid".
Mr Luca denounced "rampant Islamisation" in the country and said: "They've gained a small additional step."