"They will appear in court in Tunis on June 5... The trial will be an open hearing," Souheib Bahri told AFP, information confirmed by French consular officials in Tunis.
They will be tried for "public indecency" and an "attack on public morals", crimes both punishable by six months in jail in socially conservative Tunisia, where the coalition government is headed by an Islamist party.
They risk another 15 days in detention for offences against the Tunisian authorities.
They were arrested on Wednesday as they staged a topless protest outside the central courthouse in Tunis, the first such protest organised by radical feminist group in the Arab world.
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Their demonstration was held to demand the release of Amina Sboui, an 18-year-old Tunisian activist with their group who was detained earlier this month after protesting against Tunisia's main Salafist group and allegedly painting the word "Femen" on a wall near a cemetery in Kairouan.
Sboui, better known by her pseudonym Tyler, went on trial on Wednesday for illegal possession of pepper spray -- for which she received a fine -- amid tensions outside the court, where dozens of angry Islamists demonstrated against the topless protests.
The judge ordered that she be remanded in custody, to face separate charges next week of indecency and desecrating a cemetery, crimes punishable respectively by six months and two years in jail.