As many as 2,000 supporters of Yulia Tymoshenko marched in Kyiv as Ukraine's Specialized Supreme Court resumed hearings on the appeal by the former prime minister of her conviction for abuse of power.
The demonstrators demanded Tymoshenko's immediate release from the seven years in prison that she was sentenced to in October following her conviction in connection with natural gas deals wth Russia when she was prime minister in 2009.
Tymoshenko's supporters, as well as the European Union and United States, say she is a victim of persecution by her political enemies.
The court has not indicated when it could issue a decision.
The chairman of the opposition Front of Changes party, Arseniy Yatsenyuk, said that Tymoshenko also plans to appeal to the European Court of Human Rights in Strasbourg.
A second trial of Tymoshenko, for alleged tax evasion, is due to resume September 11.
Based on reporting by UNIAN and Interfax