Rallies were held in Ukraine on Saturday in opposition to President Viktor Yanukovych, calling for the release of former prime minister Yulia Tymoshenko from prison.
The European Court of Human Rights ruled in April that aspects of Ms Tymoshenko's detention were unlawful. She was sentenced to seven years in prison in 2011 for abuse of power.
Deutsche Welle reports the rallies were organized by Batkivshchyna (Fatherland), UDAR (Punch) and Svoboda.
The three parties said on Saturday they would work together to defeat Mr Yanukovych in the next election in 2015, where he is expected to seek a second term as president.
Ms Tymoshenko was a leader of the Orange Revolution protests of 2004. She is also on trial on new charges of embezzlement and tax evasion in the 1990s.
The European Union has delayed signing a trade agreement with Ukraine until she and several Cabinet allies are released.
Mr Yanukovych's Party of the Regions also held its own rally in Kiev on Saturday to condemn the rise of "neo-fascism" in Ukraine.