Three European activists with the women's topless protest group Femen, jailed for four months for baring their breasts in Tunis, will appeal their sentence on Friday, their lawyer said.

"The appeal hearing will take place on June 21," Souheib Bahri told AFP on Tuesday.

The three young women, two French and one German, were handed the four-month jail sentences last Wednesday for their bare-breasted protest on May 29, a first in the Arab world by Femen activists.

They staged their controversial demonstration in support of Amina Sboui, a detained Tunisian activist from the radical women's group.

France, Germany and the European Union have all expressed regret at the severity of the sentences.

Sboui was arrested for painting the word "Femen" on a wall near a cemetery in Kairouan last month, in protest against a planned gathering of radical Salafists in the historic Muslim city south of Tunis.

She is still in custody waiting for the judge to decide whether she will face charges of indecency and desecrating a cemetery.