(ANSA) - TRIESTE - Mikheil Saakashvili, the former Georgian president turned opposition leader in Ukraine, walked free after a court in the Ukrainian capital refused to sanction his arrest, vowing to push for a peaceful government change. Saakashvili was arrested Friday on allegations that he colluded with Ukrainian businessmen tied to Russia to topple President Petro Poroshenko, accusations Saakashvili rejected.

"I consider myself a prisoner of Ukrainian oligarchs", he said in an apparent reference to the business background of Poroshenko. The court's verdict marked a defeat for Poroshenko.

On Sunday, thousands of Saakashvili's supporters marched across Kiev, demanding his release and calling for Poroshenko to be impeached. Yulia Tymoshenko, a former prime minister who leads an opposition party, attended the hearing in a show of support for Saakashvili.

Saakashvili was a key figure in the 2003 Rose Revolution protests that drove Georgian President Eduard Shevardnadze from office. He served two terms as Georgian president in 2004-2013, winning broad acclaim for his anti-corruption efforts, but drawing criticism over a disastrous war with Russia and what his opponents saw as an authoritarian streak.

Poroshenko named him the governor of Ukraine's Odessa region in 2015, but Saakashvili resigned the following year, claiming that Poroshenko and other officials were impeding anti-corruption reforms, and became a strong critic of his former patron. (ANSA).