Kyiv and Moscow are reportedly preparing a prisoner exchange that would see each side swapping 33 detainees, possibly including Ukrainian sailors captured by Russian forces late last year.

RBK media group, citing unnamed sources in Russia late on August 22, said the swap of 33 Ukrainian citizens held in Russia for 33 Russian citizens held in Ukraine could occur soon.

Kremlin spokesman Dmitry Peskov confirmed to RBK that Moscow and Kyiv were negotiating a prisoner exchange, but he did not elaborate.

One of the sources told RBK that Russian journalist Kirill Vyshinsky, who used to be a Ukrainian citizen and is being held in Ukraine on high-treason charges of high, was not included in the exchange because Moscow wants his outright release.

It is also not clear if Ukrainian film director Oleh Sentsov would be among the individuals set for exchange. Sentsov, who openly protested Russia's illegal annexation of Ukraine's Crimea in 2014, is serving 20-year prison term in Russia on terrorism charges, which he and his supporters have rejected.

The sources told RBK that Ukrainian Ombudswoman Lyudmyla Denisova is in Moscow to work on the exchange, while her Russian counterpart, Tatyana Moskalkova, is on vacation until August 26.

Also on August 22, Russian lawyer Valentin Rybin told the TASS news agency that his three clients being held in Ukraine -- Russian citizens Maksim Odintsov, Aleksandr Baranov, and Yevgeny Mefyodov -- were going through judicial procedures in preparation for the exchange 'in the nearest future.'

On August 21, the Kommersant newspaper quoted sources close to Ukrainian President Volodymyr Zelenskiy as saying that the exchange could take place by the end of August and among the Ukrainians set to be transferred to Kyiv could be 24 Ukrainian sailors detained by Russian forces in November near the Kerch Strait close to Russia-annexed Crimea.

The Moscow-based Memorial human rights center said this week that five Ukrainians held in Russia -- Volodymyr Balukh, Stanislav Klykh, Oleksandr Kolchenko, Pavlo Hryb, and Mykola Karpyuk -- had been transferred from labor camps in several different regions to the Lefortovo detention center in Moscow, possibly in advance of an exchange.

Kyiv has said that Russia illegally holds about 150 Ukrainian nationals on its territory. Ukrainian officials mentioned that figure when talking about the list of prisoners prepared for possible exchange by the two countries' ombudswomen in July.

The list of Russian citizens set for the swap has never been made public.

The United States and European Union have called on Russia to free dozens of Ukrainian citizens imprisoned in Russia, Moscow-annexed Crimea, and parts of eastern Ukraine that are controlled by Russia-backed separatists.

Russia seized control of Ukraine's Crimea region in March 2014, after sending in troops and staging a referendum dismissed as illegal by at least 100 countries. Moscow is also backing separatists in a war against Ukrainian government forces that has killed more than 13,000 people in eastern Ukraine since April 2014.

With reporting by RBK, Interfax and Kommersant

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