Two members of the Moscow-based Pussy Riots band, Nadezhda Tolokonnikova and Maria Alyokhina, were seriously assaulted at a fast food outlet by local youths in Nizhny Novgorod on Thursday.
The two women, who were freed from prison shortly before the 2014 Winter Olympic games in Sochi, were reportedly in the city to meet the inmates of a local women's prison.
The unidentified assailants threw metal objects at the women as they were eating, leaving Alyokhina with "a cut to her forehead", their lawyer said, media repored.
They raised slogans, flashed banners and filmed the entire incident. One held up a placard saying: "Dirty whores, get out of the city."
The women have filed reports with the police, their lawyer said.
Meanwhile, Amnesty International, in a statement, condemned the violent nature of the attack.
"The Russian authorities must not tolerate such attacks on peaceful activists. They must launch a prompt, impartial and independent investigation into this and all such incidents, and bring those responsible to justice," said Sergei Nikitin, director of Amnesty International's Moscow office.
The outspoken feminist band has been at the centre of strong aspersions since its inception.
The women have been arrested several times in recent weeks while protesting outside the court trying the 2012 Bolotnaya Square riot case in Moscow and during the Winter Olympics in Sochi.
