Amnesty International has urged Russia to release three members of the all-woman punk band Pussy Riot, who were detained in February after the group stormed into Moscow's main cathedral to sing a protest song against President-elect Vladimir Putin.
The group takes inspiration from the "riot-grrrl" movement of the 1990s, which began in Olympia, Wash.
Amnesty said the three denied taking part in the protest, launched by other members of the group who entered Christ the Savior Cathedral on February 21 and sang "Holy Mother, Throw Putin Out" wearing multi-colored masks.
Maria Alekhina, Nadezhda Tolokonnikova and Yekaterina Samusevich face up to seven years in prison if they are found guilty of hooliganism following the performance, which criticized the Russian Orthodox Church's support for Putin.
They were the only three arrested after the protest.
"Even if the three arrested women did take part in the protest, the severity of the response of the Russian authorities -- the detention on the serious charge of hooliganism -- would not be a justifiable response to the peaceful ... expression of their political beliefs," Amnesty said in a statement released on Tuesday.
The protest lasted a few minutes, caused minimal disruption and did not damage the building, the human rights group said.
Russia should recognize people's right to freedom of expression "and release them immediately and unconditionally," Amnesty added.
Russia's Orthodox Church initially called for mercy for the protesters but later demanded harsh punishment for inciting hatred on grounds of religion.
The church said in a recent statement it was under attack from "anti-Russian forces," citing the Pussy Riot protest and media allegations against Patriarch Kirill.
The church's support for former KGB spy Putin, whose 12-year rule has been described by Kirill as a "miracle of God," has angered many members of the anti-Putin protest movement that has sprung up in the past few months.