Social networks across France responded angrily to the news a 21-year-old woman was beaten up by a gang of girls and young women for the crime of wearing a bikini in a park. Authorities are yet to have identified the attackers but The Independent reports commentators assume they were Muslims.

According to police the young victim was sunbathing with two friends in the Parc Léo Lagrange in Reims, northern France, last Wednesday when one of her five female attackers verbally abused her for “immorally” exposing so much flesh in a public place. The sunbather shouted back at which point the other girls and young women moved in, slapping and punching her.

Passers-by intervened to protect the badly bruised victim.

The attackers, aged 16 to 24, were soon arrested. The three oldest were remanded to appear in court in September, the remaining two girls, aged 16 and 17, face further questioning.

Authorities have not named the assailants but have said they all come from housing estates with large Muslim populations. Although police told L’Union newspaper that the victim was unable to confirm her assailants were motivated by “religious opinions”, bloggers in France have cited the incident as the latest example of the radical Islamic threat to French values.

The mayor of Reims, Arnaud Robinet, said: “We have to be very careful not to jump to conclusions. All the same, I can understand why people have assumed that this attack had religious motives. If that turns out to be the case, it is a very serious incident.”

In response to the attack a demonstration was organised. Wearing bikinis and other bathing costumes protesters rallied in the park where the beating took place.

Faced with drizzle and cold winds only small number showed up, but across France hundreds responded to a Twitter appeal by the anti-racist organisation SOS Racisme to post images of themselves or others wearing skimpy bathing costumes in public places using the hashtag ‘#jeportemonmaillotauparcleo’ (I wear my swimsuit in Park Leo).

#jeportemonmaillotauParcLeo ! La France est un pays libre. Les femmes y sont libres. ça te gêne? Change de pays. pic.twitter.com/5ObVaxG6WQ — Grégory Herpe Photo (@GregoryHerpe69) July 27, 2015

Translation: “France is a free country. Women there are free. It annoys you? Change country.”

Translation: “Winston will be there, he landed in Normandy today!”