"I am appealing to the crown prince of Saudi Arabia, Mohammed bin Salman Al Saud. Your Royal Highness, a woman who is deeply in love and is worried about her husband's future is begging you for help," Marchenko said in a video address.
"Your Royal Highness, your country and you personally have historically had close relations with Great Britain and as someone with a power to influence decisions made in London you could use this leverage and ask Prime Minister Boris Johnson to influence President [of Ukraine Volodymyr] Zelenskyy and have my husband exchanged for British nationals who have been taken as prisoners of war by Russian and DPR forces in Ukraine," Marchenko suggested.
Earlier in the day, Marchenko released another video, calling on the families of two suspected British mercenaries detained by the Russian forces to ask their government to demand a prisoner exchange of the British nationals for her husband.
The 67-year-old Medvedchuk, the leader of 'The Opposition Platform - For Life' party, was detained by the Ukrainian Security Forces on 12 April. Ukraine's President Zelensky suggested that Medvedchuk be exchanged for Ukrainian POWs taken by the Russian army. Moscow has criticised Medvedchuk's persecution and called it "politically motivated". Prior to his arrest earlier this week, Medvedchuk had been under house arrest facing "treason" charges levelled against him in 2021 over his business activities in Crimea. In February, he managed to escape and went into hiding.