A detained Belarus opposition leader prevented officials from forcibly expelling her into Ukraine by tearing up her passport and throwing it out of a car window at the border, colleagues who travelled with her have said.
On Monday Maria Kolesnikova was forced into a van by masked men in Minsk.
She is one of three women who joined forces to challenge President Alexander Lukashenko in August's election.
Mass protests erupted after the disputed vote.
"She was pushed into the back seat (of the car), she yelled that she wasn't going anywhere," Ms Kolesnikova's colleague Anton Rodnenkov told a news conference in the Ukrainian capital, Kiev, on Tuesday.
Mr Rodnenkov said he and a colleague had been taken to the border with Ms Kolesnikova but she refused to cross. The two men told journalists they did not know where she was now.