Saakashvili could be extradited to Georgia where he is wanted on corruption charges.
Protestors this weekend had four main demands: impeach Poroshenko, release Saakashvili, set up an independent anti-corruption court that would have cases brought by NABU and sack Prosecutor General and close Poroshenko ally Yuriy Lutsenko, who has been the tool used by the president in his campaign against Saakashvili.
Prosecutors had asked to keep Saakashvili under house arrest, but the judge turned it down to the applause of Saakashvili's supporters.
Mr Saakashvili's supporters scuffled with police outside the court building.
Saakashvili, who was refusing food to protest the arrest, said that the first thing he now wants is to get back home and eat.
While the Saakashvili protests are not particularly significant by themselves, their importance lies in how they become rallying points for other opposition movements.
"Poroshenko is an oligarch, and it's silly to expect him to fight corruption", Shapovalov said.
Activists of the Right Sector, a far-right nationalist group, and veterans of the war against pro-Russia separatists in eastern Ukraine joined the rally.
One of the options to destabilize the situation in Ukraine may be attempts by the Russian special services to eliminate Saakashvili and Dangadze, the prosecutor added.
Saakashvili was a key figure in the 2003 Rose Revolution protests that drove Georgian President Eduard Shevardnadze from office. Poroshenko this summer rescinded his Ukrainian citizenship while Saakashvili was out of the country, leaving Saakashvili stateless.
Ukrainian President Petro Poroshenko rewarded Saakashvili for his efforts by appointing him governor of the important Black Sea region of Odessa in 2015 before the two men fell out and his Ukrainian passport was annulled. He was out of the country when he lost Ukrainian citizenship, but forced his way into Ukraine in September, barging across the border with Poland with the help of a crowd of supporters.
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