A member of the Russian punk protest band Pussy Riot has been barred from leaving Russia, a colleague says.

Maria Alyokhina was not allowed to leave Moscow for London, Pyotr Verzilov tweeted on August 8.

"The Federal Security Service's border service told her that she is barred from leaving the country," Verzilov wrote.

On August 7, Alyokhina and two other activists staged a protest in front of the headquarters of the Federal Penitentiary Service (FSIN) in Moscow.

The activists hung a red poster on the building bearing "FSIN = GULAG," as well as several photos of men in prison uniforms who appeared to have been beaten. Each photo had penitentiary numbers and locations.

The action was meant to protest against what activists called the beating and torture of inmates by prison guards across Russia.

Alyokhina and two other members of Pussy Riot came to prominence after they were convicted of "hooliganism motivated by religious hatred" for a stunt in which they burst into Moscow's Christ the Savior Cathedral and sang a "punk prayer" against Vladimir Putin, who was prime minister and campaigning for his return to the presidency at the time.

Alyokhina and bandmate Nadezhda Tolokonnikova were close to the end of their two-year prison sentences when they were freed in December 2013, under an amnesty they dismissed as a propaganda stunt to improve Putin's image ahead of the 2014 Sochi Winter Olympics.