Russian and Ukrainian negotiators appear to have reached an agreement for the release of imprisoned filmmaker Oleg Sentsov, Radio Liberty reports. The provisional agreement would see Sentsov and another Ukrainian activist arrested with him traded for two Russian military intelligence officers captured in eastern Ukraine’s Donbas region. The Donbas is home to the self-declared Donetsk People’s Republic which seeks union with the Russian Federation.

While Russia repeatedly denies its direct military involvement in Ukraine and officially calls the soldiers rogues, the country still desires for the two captured officers, Alexandr Aleksandrov and Yevgeny Yerofeyev, to return to their native country. The undeclared war has dictated a complex legal situation for the soldiers as well as for Sentsov and his alleged accomplice Aleksandr Kolchenko.

Ukrainian filmmaker Oleg Sentsov, imprisoned in Russia, gives the peace sign during his August, 2015 trial.

Sentsov, best known for his 2011 film Gámer, and Kolchenko have had their case be the subject of much international attention. While both he and the main witness testifying against him described being tortured during the case, neither claim was investigated by Russia’s military courts. A Supreme Court appeal late last year also did not end in his favor, with the court ruling in favor of a 20-year sentence for the filmmaker on alleged terrorist activities.

The case has been declared by many international organizations to be fabricated and the trial unfair. The Voice Project has advocated for Sentsov’s release since October of last year.

Volodymyr Ruban, the head of Ukraine’s Center for the Release of Prisoners, confirmed that talks began last year on the subject of trading Sentsov for the two Russian soldiers, but that Ukrainian negotiators instead pushed for a “two-for-two” trade.

In recent negotiations in Minsk, Belarus, Russian and Ukrainian negotiators agreed to such a trade, although it will take some time.

Enacting the agreement will have to wait until Ukrainian courts officially charge the two Russian officers. “Under certain guarantees, the diplomats will exchange not the hostages, not prisoners of war, but convicts and each of them will be brought to his country where one would still have to receive a pardon,” Ruban said.

Sentsov and Kolchenko famously sang the Ukrainian national anthem in the cell when sentenced in October 2015.

The Voice Project will continue to provide updates on this story as it develops.