The southern French city of Cannes has banned full-body swimsuits -- known as burkinis -- from the beach, citing public order concerns.
In an order signed by Mayor David Lisnard in late July, beach access is denied to anyone "lacking correct attire, respectful of good customs, and secularism."
It notes that swimwear "manifesting religious affiliation in an ostentatious way, while France and its religious sites are currently the target of terrorist attacks, could create risks of trouble to public order."
Anyone caught flouting the rule, which is in effect through August 31, could face a fine of 38 euros ($42).
Critics said they would challenge the ban in court, calling it discriminatory.
France is on high alert following a series of incidents, including a July 14 attack claimed by the Islamic State group that killed 85 people. On July 26, a priest was killed in his church in northwestern France by attackers who had proclaimed their allegiance to the extremist group.
Earlier this week, a private waterpark near the Mediterranean port city of Marseille canceled a burkini-only day after being subjected to criticism.
In 2011, France became the first country in Europe to ban the full-face Islamic veil in public spaces.