
Medvedchuk made the appeal to Russian president Vladimir Putin and Ukrainian president Volodymyr Zelensky in a video published by the SBU security service on Facebook.
It was unclear how freely Medvedchuk was speaking in the video.
He said was a making a “plea for the Ukrainian side to exchange me for the defenders of Mariupol and its citizens who are there today have no opportunity for a safe exit through a humanitarian corridor”.
Medvedchuk, the leader of the Opposition Platform – For Life party, is an ally of Putin.
Medvedchuk had been placed under house arrest last year to face treason and terrorism financing charges, which he denies.
He escaped a few days after the Russian invasion began in February, but was later captured by Ukraine.