Riot police have been deployed to the streets of the Ukrainian capital Kiev amid a stand-off with hundreds of protesters who had blocked a police van carrying an arrested politician.
- Mikheil Saakashvili, the former president of Georgia who has emerged as an anti-corruption campaigner, urged Ukrainians Sunday to set up a protest camp in Kiev's main square if parliament fails to adopt a law on presidential impeachment within a week.
On Tuesday morning, Ukraine's Security Service (SBU) agents from its Alpha unit barged into the opposition figure's apartment in Kiev.
"I will leave here only with the Ukrainian people, only as a victor", the former Georgian president told supporters outside the Supreme Rada late Tuesday afternoon. He then served as president for almost a decade.
He resigned as Odessa governor in 2016, complaining that his efforts to root out corruption suffered official obstruction.
On Sept. 10, a defiant Saakashvili crossed into Ukraine from Poland without showing the necessary documents to the border guards.
His stand-off with Mr Poroshenko ignited long-simmering popular discontent with the slow pace of the president's much-promised reforms.
Earlier in the day, the Security Service of Ukraine said Saakashvili was arrested on suspicion of "aiding members of criminal groups and covering up their criminal activity".
Ukraine's general prosecutor Yuriy Lutsenko accused Saakashvili and his allies of receiving $500,000 (420,000 euros) from Russian sources to fund the protests against the Ukrainian government.
Saakashvili has spearheaded several protests in Kiev, but they typically drew fewer than 4,000 people.
"All the rallies were financed by foreign oligarchs that aimed to seize power by illegal means", Lutsenko said.
President Vladimir Putin's spokesman said the Kremlin was "once again surprised by Kiev and once again surprised by Saakashvili". "They can make a lot of noise but most Ukrainians are wary of negative and unpredictable consequences of a new Maidan".