Russian news agencies quoted Deputy Foreign Minister Andrei Rudenko as saying that Russia is studying a potential prisoner swap with Ukraine once the Ukrainian detainees are tried.
He said, "We will look into all this after the trial of those who surrendered and after the verdict is pronounced," adding, "Before that, talking about the exchange is premature."
Last week, the last Ukrainian defenders of the strategic city of Mariupol, holed up for weeks at the Azovstal steel plant, surrendered.
Nearly 4,000 Ukrainian soldiers have been captured in this port city, according to the Russian Defense Ministry.
Ukrainian authorities want to organize a prisoner exchange, but Moscow has long indicated that it views some of them as belonging to the Azov Brigade, not as soldiers but as neo-Nazi fighters who committed war crimes.