President of Ukraine Petro Poroshenko has said that world leaders are being involved in solving the painful problem of the liberation of Ukrainians, who are illegally retained by Russia.

"The whole world stood in support of Volodymyr Balukh who, in protest, is already hunger striking for 89 days; Oleh Sentsov, who is hunger striking for 34 days; Oleksandr Shumkov, who is hunger striking for 23 days - and more than 70 Ukrainian political prisoners who are forcibly kept and tortured by the Kremlin regime," Poroshenko wrote on his Facebook page on Saturday.

"I raise the issue of the release of Ukrainian hostages in all international negotiations, and to my call world leaders are being involved in solving this painful problem - the pressure on Russia continues. We demand freedom from the Kremlin for Ukrainian political prisoners," the Ukrainian president added.