Ukraine's President Volodymyr Zelensky on Friday offered to hand Moscow a detained Russian state media journalist in exchange for Ukrainian film director Oleg Sentsov who is behind bars in a Russian Arctic penal colony.
Russia and Ukraine are in the midst of sensitive talks on a prisoner exchange following the first-ever phone call between Zelensky and Russian President Vladimir Putin last week.
Filmmaker Sentsov, Ukraine's most famous political prisoner, is serving a 20-year sentence in a Russian penal colony for planning "terrorist attacks" in Crimea, which was annexed by Russia in 2014.
Kiev says the charges are politically motivated and last year Sentsov staged a hunger strike and went 145 days without solid food.
Zelensky said Friday that Kiev was ready to release 52-year-old Kyrylo Vyshynsky, a journalist working for Russia's RIA Novosti state news agency, in exchange for Sentsov.
Vyshynsky, who holds both Ukrainian and Russian citizenship, was detained by Kiev in 2018 and is awaiting trial on treason charges.
"If we are talking about goodwill and want (a prisoner swap) to happen in the nearest future, we are ready to exchange Kyrylo Vyshynsky," Zelensky said during a visit to Ukraine's defence ministry.
A Kiev court later Friday extended Vyshynsky's detention for another two months, prompting condemnation from Moscow.
"A shame and a disgrace," Russian foreign ministry spokeswoman Maria Zakharova wrote on Facebook.
Russia's human rights ombudsman Tatyana Moskalkova appeared to shoot down Zelensky's offer, saying Vyshynsky should be released "without any preconditions".
"He himself is categorically against any swap," she said in a statement.
Zelensky, who has been in office since May after winning elections earlier this year, has said that Putin has proposed exchanging all the countries' prisoners.
Putin's spokesman Dmitry Peskov on Thursday confirmed that swapping "all" prisoners would be ideal but the sides had to agree what that meant.
He said the return of Vyshynsky "could be a great first step".
This week a Russian court prolonged the detention of 24 Ukrainian sailors captured last year near Crimea, in a move decried by Kiev.
A senior Ukrainian presidential official said this week that Kiev and Moscow had agreed to exchange a certain number of prisoners over the next month.
The two ex-Soviet countries have been locked in a confrontation since 2014 when Moscow annexed Crimea and supported an insurgency in eastern Ukraine.
Around 13,000 people have been killed in the conflict.