Ukrainian authorities accuse Mikheil Saakashvili, Georgia's former president and now an anti-corruption crusader in Ukraine, of colluding with Ukrainian businessmen to topple President Petro Poroshenko.
Saakashvili said he will not turn himself in, though prosecutors were welcome to see him at the camp outside the Supreme Rada where about 100 supporters gathered.
"I'm ready to host their investigators here at the camp," he said. "From the very beginning they refused to register my party, then stripped me of my citizenship, then lied. Shame on you."
It was the police's second unsuccessful attempt to arrest Saakashvili in as many days. On Tuesday, police detained him at his home, but he escaped with help from crowds who had gathered to protest.
Protester Igor Ognyov, from the eastern city of Sumy, told The Associated Press that the police stormed the camp before dawn on Wednesday.
"They burst into the tent and started beating everyone with their hands and batons," said Ognyov, whose head was bandaged and his face covered with blood.
Two protesters and 11 officers were injured in Wednesday's scuffles in Kiev, police said.
The efforts to detain Saakashvili have raised fears that Ukraine could be facing its most acute political crisis since the 2014 revolution.
Poroshenko named Saakashvili as governor of the Odessa region in 2015, but he stepped down the following year after falling out with the president. Earlier this year, Poroshenko stripped Saakashvili of Ukrainian citizenship while he was out of the country, but the former Georgian president returned in September, helped by supporters.
Saakashvili has won broad popularity in Ukraine with his fiery campaign against official corruption, riding a wave of public frustration over Poroshenko's failure to uproot endemic graft. He has staged a series of rallies calling for the president's resignation, but they haven't produced any visible impact.
Prosecutor General Yuri Lutsenko says his office has evidence that Saakashvili's representative received $500,000 to finance protests from Ukrainian businessmen with ties to Russia.
Saakashvili rejected the accusations and said there has long been hostility between him and Russian President Vladimir Putin.
Inna Varenytsia contributed to this report from Kiev, Ukraine.
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