Ukraine's prosecutor-general says opposition figure Mikheil Saakashvili has been arrested.
Yuriy Lutzenko made the announcement late Friday on his Facebook page. Saakashvili, the former president of Georgia who later moved to Ukraine, has been a leader of opposition to Ukrainian President Petro Poroshenko, especially criticizing the president's failure to halt corruption in the country.
A Saakashvili spokeswoman, Daria Chizh, told The Associated Press that he had been taken to a detention facility of the SBU, the national security service.
Saakashvili became governor of Ukraine's Odesa region in 2015 and was granted citizenship. But he left that post, complaining that Poroshenko was blocking his anti-corruption efforts, and was stripped of his Ukrainian citizenship in August.
He had earlier lost his Georgian citizenship and he was outside Ukraine when Poroshenko rescinded his status. That left him stateless, but he returned to Ukraine in September, boldly barging across the border with Poland aided by a crowd of supporters.
Since then, he has pushed to galvanize opposition to Poroshenko and other government figures he contends are corrupt. Although his support appeared to be comparatively small, he was able to gather several thousand people for a protest march last week.
On Tuesday, police tried to arrest Saakashvili at his apartment building. He climbed out on the roof and threatened to jump, but police grabbed him and took him to a van. The van was surrounded by a throng of supporters who eventually were able to free him. An attempt to arrest him at a protest tent camp near the Ukrainian parliament also failed.
Lutsenko says his office has evidence that Saakashvili's representative received $500,000 to finance protests from Ukrainian businessmen with ties to Russia. Saakashvili rejects the allegations, pointing to his long record of opposition to Russian President Vladimir Putin.
Saakashvili is also wanted in Georgia on charges of abuse of office during his 2004-13 presidency.