Saakashvili in Kyiv on February 9
Ukraine's State Border Guard Service said that the Georgian-born politician was removed from Ukraine on February 12 because he was in the country illegally.
"The criminal case against me is a complete lie. Putin and Poroshenko and Ivanishvili want to get rid of me," Saakashvili said in a Facebook video in reference to Russian President Vladimir Putin, Ukrainian President Petro Poroshenko, and former Georgian Prime Minister Bidzina Ivanishvili.
Earlier in the day, Ukrainian security forces detained Saakashvili at a Georgian restaurant near the headquarters of his New Forces party in the capital, Kyiv, before being transported to a nearby airport.
A post on Saakashvili's Facebook page said he was held by unidentified men in masks and taken away. "The kidnappers were in three white Volkswagen minivans," it said.
A short video clip showed gun-toting men in camouflage struggling with a man inside a restaurant and shouting at him to lie down and stay down. One of the armed men kicks the man when he is prone.
"This person was on Ukrainian territory illegally and therefore, in compliance with all legal procedures, he was returned to the country from where he arrived," Oleh Slobodyan, a spokesman for the Ukrainian State Border Guard Service said.
He added that border guards "had to defend themselves using force" against some individuals associated with Saakashvili. Slobodyan gave no further details.
Polish border police confirmed in a statement that Saakashvili had arrived in Warsaw and that "the basis for the admission decision was a readmission application submitted by the National Migration Service of Ukraine to the commander-in-chief of the Border Guards."
"Taking into account the fact that M. Saakashvili is a spouse of a citizen of a member state of the European Union, the request of the Ukrainian side was considered positively," it added.
Saakashvili's wife, Sandra Elisabeth Roelofs-Saakashvili, was born in the Netherlands and has Dutch citizenship.
Unlike the street protests that allowed Saakashvili to escape police custody in December, there were no immediate signs of public demonstrations against the move by security officials.
"We need to react calmly" to the expulsion, Saakashvili said, adding that Poroshenko "is not a president or a man, but a sneaky huckster who wants to ruin Ukraine."
Comment: As if Saakashvilli is any different himself!
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"This all shows how weak they are. We will defeat them," he said.
David Sakvarelidze, an ally of Saakashvili, vowed opposition to Poroshenko would continue unabated.
"It was a mistake by Poroshenko and his people to abduct Saakashvili. Poroshenko must understand that even if Mikheil is out of the country, his plan to hold rallies on February 18 will be implemented no matter what. I do not know exactly where they keep him now," Sakvarelidze said.
The developments came a week after a court rejected an appeal by the former Georgian president for protection against possible extradition.
Saakashvili's backers expressed concern that the ruling increased the chances that he would be handed over to Georgia, where he is wanted on charges he says are fabricated, or deported to another country.
The reformist president of Georgia from 2004-2013, Saakashvili lost his Georgian citizenship in 2015, when he accepted Ukrainian citizenship and Poroshenko's offer of a job as governor of the Odesa region.
But he resigned from the post in November 2016, accusing the government of undermining his efforts to fight corruption and carry out reforms.
Saakashvili has become an outspoken opponent of Poroshenko, who came to power after Moscow-friendly President Viktor Yanukovych fled amid massive protests known the Euromaidan in 2014.
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In July 2017, Poroshenko stripped Saakashvili of his Ukrainian citizenship while he was abroad.
In September, Saakashvili defied a border blockade and crossed from Poland into Ukraine, where he has been leading anti-Poroshenko protests and struggle against the state in a series of court cases.
Ukrainian authorities accused Saakashvili of abetting an alleged "criminal group" led by Yanukovych, and claim the protests he has led are part of a Russian plot against the government in Kyiv.
Saakashvili has denied all the charges, calling them "absurd" and politically motivated.
Christopher Miller is a correspondent based in Kyiv who covers the former Soviet republics.
I hope Polish government won't be stupid enough to offer him much support, but I feel I'm a bit naive there. Anyway, it's a matter of time since he starts his own party, and tries to overthrow the government somehow. That's his style. His, and his CIA masters.