Moscow has indicated it is considering freeing four imprisoned Ukrainians, including filmmaker Oleh Sentsov, who were convicted by Russian courts on charges related to Russia's forcible annexation of Crimea and derided by critics as politically motivated.
The Russian Justice Ministry said in a statement on April 8 that it had asked the Federal Penitentiary Service to prepare documents for the transfer of the four men back to Ukraine following a March 10 request from Kyiv.
However, the ministry said any final decision to hand over Sentsov, Hennadiy Afanasyev, Oleksandr Kolchenko, and Yuriy Soloshenko would be made by Russian courts.
Ukrainian President Petro Poroshenko earlier this year indicated he would consider exchanging two Russians captured in eastern Ukraine for some of the Ukrainians being held in Russia.
Dubbed the "Crimean terrorists" by the Russian media, Sentsov, Afanasyev, and Kolchenko were arrested soon after Russia's March 2014 annexation of the Ukrainian Black Sea peninsula.
Russian prosecutors accused Sentsov and Kolchenko -- a left-wing activist -- of plotting sabotage and terrorist attacks around Crimea. They built their case largely on testimony from Afanasyev, another activist, although he has recanted and said he was tortured into testifying against the two.
A court in the southern city of Rostov-on-Don convicted Sentsov and Kolchenko in August and sentenced them to 20 and 10 years in prison, respectively.
Afanasyev was sentenced to seven years in prison.
Soloshenko was convicted in October by a Moscow court of espionage. Russia's main security agency insisted he was trying to buy secret components for an air-defense missile system used in both Russia and Ukraine.
Sentsov, whose 2011 film Gamer garnered international acclaim, is among the highest-profile prisoners being held in Russia, and his case drew protests from the European Union and many European filmmakers.
Sentsov told the Russian court that a "trial by occupiers cannot, by definition, be fair."
Russia is also holding Ukrainian military pilot Nadia Savchenko, who was sentenced by a Russian court last month to more than 20 years in prison after finding her complicit in the deaths of two Russian journalists covering fighting in eastern Ukraine in June 2014.
Savchenko, who is regarded by Ukrainians as a symbol of defiance against Russian aggression, has refused to recognize the validity of her detention and reportedly has launched a dry hunger strike in prison.
In a Facebook post on April 8, one of Savchenko's defense lawyers, Ilya Novikov, said after visiting her in prison that her health was beginning to worsen, and that a prison official had warned they would consider force-feeding her.
Novikov also said Savchenko's prison cell was being monitored round-the-clock by video cameras, and that she had stopped using the shower or the washroom in order, he said, "not to give the meathead media any reason to speculate."
A UN resolution refusing to recognize Russia's seizure of Crimea from Ukraine passed overwhelmingly, and Kyiv and NATO accuse Russia of continuing to arm and back -- including with troops -- armed pro-Moscow separatists holding swaths of eastern Ukraine.