Former Georgian president Mikheil Saakashvili and hundreds of his supporters forced their way into Ukraine on Sunday in a bid by the firebrand politician to reclaim his citizenship stripped by President Petro Poroshenko after they fell out.
Saakashvili says he wants to return to challenge that decision in court and get back into politics.
An AFP reporter saw the one-time regional Ukraine governor and his supporters enter from Poland's Medyka border crossing, pushing aside Ukrainian border guards who had turned him back just hours earlier.
"They did it against all the rules, what's happening here?" Saakashvili told reporters in Medyka when he was initially refused entry, adding: "We hope that we can still break through."
At that point hundreds of his supporters chanting "Misha, Misha" -- a diminutive of his name -- forced their way into Ukraine with Saakashvili, who now risks extradition to his native Georgia.
Around 1,500 supporters marched with the exiled ex-Georgian leader on the Ukrainian side of the border before he hopped into a car bound for the western city of Lviv, where around 500 supporters greeted him on his arrival.
Saakashvili was then reported to be meeting with Lviv Mayor Andriy Sadovyi late Sunday night.
The border-breach drew ire in Kiev, with the interior ministry saying in that 11 policemen and five border guards had been injured in clashes with Saakashvili supporters, suggesting prison terms for those responsible.
"By fighting for power, supporters of Saakashvili are destroying the state," Yuriy Lutsenko, Ukaine's Prosecutor General, wrote on Facebook.
Tbilisi on Tuesday asked Kiev to extradite Saakashvili to face charges of misappropriation of property and abuse of office among others.
Saakashvili denies the accusations, branding them a political witch hunt.
He says Georgia's extradition request was driven by "oligarchs" who fear his presence in Ukraine, where he fought corruption.
Earlier Sunday, Ukrainian authorities blocked a Kiev-bound train in Poland carrying Saakashvili, who eventually got off and took a bus to the Medyka crossing.
Ukraine's outspoken ex-prime minister Yulia Tymoshenko threw her support behind the 49-year-old, accompanying him as he attempted to cross into Ukraine the first time.
Saakashvili said "several hundred thugs were mobilised by the Ukrainian government to stop several thousand" of his supporters waiting to greet him on the Ukrainian side.
Kiev is "panicking," Saakashvili said, adding that he did "not want to overthrow President Poroshenko" but just defend his rights.
"We believe that Mikheil Saakashvili can lead our country out of the crisis," Lyudmyla Goretska, one of thousands of supporters waiting on the Ukrainian side of the border, told AFP.
"We see what he did in his own country and that's enough for us," Goretska said of Saakashvili, who set up the Movement of the New Forces political party in Ukraine.
"The main problem in our country is corruption... We need to overcome the oligarchy."
The charismatic Saakashvili is credited with pushing through pro-Western and anti-graft reforms in Georgia which he led from 2004 to 2013.
Another supporter, Maria, 49, who declined to give her surname, said she believes "Saakashvili is the future president" of Ukraine and "will finish the war" with Russia.
Saakashvili is also wanted in his homeland for alleged abuse of power during a tumultuous nine years as president that saw him fight and lose a brief war with Russia in 2008.
He left in disgrace for Ukraine in 2015 to work for the country's pro-Western authorities as governor of the key Odessa region on the Black Sea.
But he quit in November 2016 amid a dramatic falling out with Poroshenko, who stripped him of his Ukrainian citizenship in July while he was out of the country.
Kiev justified the move by claiming that Saakashvili had provided "inaccurate information" in his citizenship application.
Saakashvili lost his Georgian citizenship when he was granted a Ukrainian passport in 2015, as the country does not allow dual nationality.
The reformer has said he now wants to go to court to get back his Ukrainian citizenship, a move that would allow him to stand for election.
"We see a roll-back of reforms in Ukraine, we see a crackdown on anti-corruption activities in Ukraine. This is very sad," Saakashvili said Friday in Warsaw.