Pussy Riot and the Greenpeace Arctic 30 could be free within days, after the Russian parliament granted both groups amnesty in a far-reaching new law.
Rights activists in Russia have greeted the news with mixed enthusiasm, with Human Rights Watch's Tanya Lokshina telling HuffPost UK that the "amnesty is no remedy for a flawed justice system".
The amnesty bill is expected to be published in the government newspaper on Wednesday evening, after it was passed by the Duma.
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Feminist punk group Pussy Riot members, from left, Yekaterina Samutsevich, Maria Alekhina and Nadezhda Tolokonnikova
The law was amended last night to include the 28 Greenpeace activists and two freelance journalists, including six Britons, who have been bailed and await charge in St Petersburg.
Pussy Riot's Nadezhda Tolokonnikova and Maria Alyokhina are in the midst of two-year sentences for staging a "punk protest" against President Vladimir Putin in Moscow's cathedral early last year.
They were convicted of "hooliganism motivated by religious hatred". A third band member, Katya Samutsevich, was released on a suspended sentence.
Earlier this year, Samutsevich told The Huffington Post UK that she could not celebrate her own freedom because she believed there had not been justice for the band.
Earlier this year, Tolokonnikova went on hunger strike to protest the "Stalinist" conditions in the Mordovia work camp where she was imprisoned, seeing other prisoners stripped naked and beaten to death.
Russian prison authorities on December 16 announced that Tolokonnikova will serve the remainder of her term at a prison hospital in Krasnoyarsk, because of the self-harm she had inflicted by her hunger strike.
Petya Verzilov, Tolokonnikova's husband, told the Guardian that his wife found it "hard to think about the Duma passing some bill, and it seems like it could never happen, so it's a big surprise for them that it does actually seem to be happening."
Greenpeace says the 26 non-Russians will almost certainly be free to return home once they are granted exit visas, but did not know when this would happen.
Ana Paula Maciel from Brazil, one of the activists, said: "Right now, my thoughts are with our Russian colleagues. If they accept this amnesty, they will have criminal records in the country where they live, and all for something they didn't do. All because we stood up for Arctic protection."
Arctic Sunrise captain Peter Wilcox, of the United States, said: "We went there to protest against this madness. We were never the criminals here."
Putin, who has been lobbied extensively by European and US leaders over the arrests, has said it was "absolutely evident that they are, of course, not pirates..." when the Greenpeace activists were originally accused of piracy. But he added: "But formally they were trying to seize this platform... It is evident that those people violated international law."
People attending a protest outside the Russian Embassy, London, organised by Greenpeace
For Pussy Riot, the Russian president had harsher words, calling their performance "an act of group sex aimed at hurting religious feelings". "We have red lines beyond which starts the destruction of the moral foundations of our society," Putin told a dinner of academics and business leaders in October last year.
"This is largely a PR project in the run-up to the Olympics," Lokshina told HuffPost UK. "Sochi 2014 is just around the corner, this gets them some good publicity. The actions against the Arctic Sunrise participants was clearly disproportionate. This is a solution that is convenient for the authorities.
"When it comes to Pussy Riot, the Supreme Court decided last week that the case against them was not well founded. So this amnesty just makes all those problems go away.
"It's not a solution, it's a deeply compromised, heavily political move."
The amnesty, which celebrates the 20th anniversary of Russia's constitution, was passed by the Russian parliament early on Wednesday. Amnesties are common in Russia on national holidays, and apply to primarily retirees, the disabled, women with children and pregnant women, and victims of the Chernobyl disaster.
It will free almost 25,000 people, but it will not include Mikhail Khordokovsky, once Russia's richest businessman, who is in jail for various frauds.
He insists the allegations against him are politically motivated.
Many of those who demonstrated at Putin's inauguration in Moscow protests will also not be released, only eight who participated will be freed, none of the allegedorganisers or those accused of violent offences will be freed.