Wife of captured Putin ally Viktor Medvedchuk called on Zelenskyy to release her husband as the Kremlin hung him out to dry

• Ukraine captured the pro-Kremlin oligarch Viktor Medvedchuk earlier this week.
• Medvedchuk's wife asked Zelenskyy to release him.

The wife of the oligarch and Putin loyalist Viktor Medvedchuk, whom Ukraine captured earlier this week, demanded President Volodymyr Zelenskyy release her husband after the Kremlin refused to trade Ukrainian prisoners for Medvedchuk's release.

Ukraine's security service said on Tuesday that it had arrested Medvedchuk as he tried to flee the country, with Zelenskyy later saying the oligarch had tried to disguise himself in military uniform.

Ukraine accused Medvedchuk, the former chairman of the pro-Russian Ukrainian Choice political party, of treason.

In a video posted to YouTube on Wednesday, Medvedchuk's wife, Oksana Marchenko, asked Zelenskyy to free her husband.

"I, Oksana Marchenko, the wife of Ukrainian parliament member Viktor Medvedchuk, request President Zelenskyy to take all the necessary measures for the immediate release of my husband Viktor Medvedchuk who is being illegally detained by the SBU," she said, referring to Ukraine's security services, according to Russia's state-run TASS news agency.

She said that her husband "neither violated Ukrainian laws nor left the country."

Her statement came as Russia declined Zelenskyy's offer on Wednesday to trade Medvedchuk for Ukrainian prisoners.

Russia is believed to have captured thousands of Ukrainian civilians, and sent many to "filtration camps" where people were reportedly fingerprinted and had data taken from their cellphones.

Medvedchuk is close to Russian President Vladimir Putin, who is the godfather of his youngest daughter, and the pair have holidayed together on the Black Sea.

But the Kremlin essentially abandoned Medvedchuk on Wednesday, with the Kremlin spokesman Dmitry Peskov saying he was "not a citizen of Russia" and had nothing to do with its "special military operation" in Ukraine, according to the state-run Interfax news agency.

"He is a foreign political figure," Peskov said.

"We don't know at all whether he himself wants some kind of participation on the part of Russia in resolving this libelous situation against him."

The UK sanctioned Medvedchuk on Wednesday, calling him a "major Ukrainian oligarch with close ties to Putin." The US had already sanctioned him in 2014 over the annexation of Crimea, calling him a "long-time proxy and close personal friend" of Putin.