Nadezhda Tolokonnikova, a former member of the punk protest band Pussy Riot, was detained in central Moscow on June 12 along with another activist after a performance in which they wore gulag-style prison uniforms and sewed a Russian flag.
Tolokonnikova posted photos of herself and Katrin Nenasheva inside a police van on Facebook.
She wrote that she and Nenasheva were detained by police on Bolotnaya Square, while wearing clothes that looked like the prison garb used since the Soviet era and sewing a flag. June 12 is the Day of Russia, a patriotic holiday.
Tolokonnikova and Pussy Riot partner Maria Alyokhina spent nearly two years in jail for a February 2012 protest in which the group burst into the country's main Russian Orthodox cathedral and sang a "punk prayer" against Vladimir Putin, who was successfully running for a third presidential term at the time.
The pair has made advocacy for improvements in prisoners' rights and prison conditions their main cause since their release in December 2013, in an amnesty they dismissed as a propaganda stunt ahead of the Sochi Winter Olympics in February 2014.
Bolotnaya Square was the scene of clashes between police and protesters on the eve of Putin's inauguration in May 2012. More than 400 people were arrested during and after the clashes and 29 were charged for their alleged part in the unrest. Some are in prison and others could still face trial.
This year, the June 12 holiday marks the 25th anniversary of Russia's proclamation of sovereignty from the Soviet Union in 1990.
