Ukraine has issued mixed signals on the fate of imprisoned ex-premier Yulia Tymoshenko, with the president hinting she could be released after a legal reform but the country's security agency filing new corruption charges against her.

Ukraine's state security service has alleged she was involved in running up a $405 million debt to Russia on behalf of the Ukrainian state while prime minister.

On Tuesday Tymoshenko was jailed for seven years for abuse of office in a trial that has outraged western governments.

Al Jazeera's Neave Barker reports from Moscow.