Greenpeace published a photograph of Madonna on its Twitter account Friday with her quote asking to "bring home" the activists.
Twenty-eight Greenpeace activists and two journalists have been detained since September after some of the activists attempted to climb an oil rig owned by Gazprom, a state-controlled energy company.
The 30 detainees were initially accused of piracy but the charge later was reduced to hooliganism, which carries a maximum sentence of seven years in prison.
The activists were moved this week to separate detention facilities in St. Petersburg, RIA Novosti said, and were scheduled to appear at a hearing Nov. 24.
Oscar-winning actress Cotillard briefly put herself into a cage Friday in Paris with a group of environmental activists to protest the detention of the Greenpeace activists in Russia, RIA Novosti reported.
British musician Paul McCartney wrote an open letter earlier in the week asking Russian President Vladimir Putin to release the activists and "intervene to bring about an end to this affair."