Madonna has urged officials in Russia to release imprisoned members of punk band Pussy Riot from prison, branding their two-year sentence "inhumane".

Nadezhda Tolokonnikova, 23, Maria Alekhina, 24, and Yekaterina Samutsevich, 29, were found guilty of hooliganism on Friday after singing a protest song aimed at President Vladimir Putin at a church in Moscow during a service earlier this year.

Madonna, who has been left stunned by the sentencing, voiced her support for the band members at her concert in the city earlier this month wearing a baclava and revealing the words "pussy riot" stamped across her back.

In a statement, she declares, "I protest the conviction and sentencing of Pussy Riot to a penal colony for two years for a 40-second performance extolling their political opinions.

"Even if one disagrees with the location or how they chose to express themselves, the sentence is too harsh and in fact is inhumane. I call on all those who love freedom to condemn this unjust punishment. I urge artists around the world to speak up in protest against this travesty. They've spent enough time in jail. I call on ALL of Russia to let Pussy Riot go free."

Madonna is not the only star to pledge her support, Kate Nash, Bjork and Paul McCartney have all spoken out against the trial.