A detained Belarus opposition leader prevented officials from forcibly expelling her at the border by tearing up her passport and throwing it out of the car window, colleagues travelling with her say.
On Monday Maria Kolesnikova had been forced into a van by masked men.
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.
Earlier on Tuesday, officials in Belarus had claimed that Maria Kolesnikova was detained while trying to cross into Ukraine.
Meanwhile, in an interview with Russian media on Tuesday, Mr Lukashenko insisted he would not step down from power.
Dozens of people were arrested on Tuesday in fresh protests in the capital, Minsk. In recent weeks thousands have faced violence and threats of arrest in demonstrations against Mr Lukashenko, who has ruled the country since 1994.
The EU has demanded the release of all political prisoners and says it is planning to impose sanctions.
Ms Kolesnikova is the last of three women leading the opposition to Mr Lukashenko to remain inside Belarus.
The main opposition leader, Svetlana Tikhanovskaya, says she won 60-70% of the poll in places where votes were properly counted. She fled to Lithuania after she was detained in August.
What happened to Maria Kolesnikova?
On Monday, witnesses saw masked men seize Ms Kolesnikova on a street in central Minsk and push her into a minibus.
Then, on Tuesday, she and opposition colleagues Anton Rodnenkov and Ivan Kravtsov were taken to the country’s border with Ukraine by men in plain clothes, Mr Rodnenov says.
But when the car reached a checkpoint between the two countries, Ms Kolesnikova prevented her deportation by tearing up her passport and throwing away the pieces, he said.
“She climbed, climbed from the car and she walked proudly to Belarusian territory,” Mr Kravtsov said, adding: “She’s really a hero. You must understand that. She’s very dedicated to what she’s doing now.”
What did Mr Lukashenko say?
Earlier on Tuesday, Mr Lukashenko told Russian reporters that Ms Kolesnikova had been held for “violating the rules on crossing the state border”.
In a sit-down interview, the long-term leader was quoted as saying he would not step down.
He conceded that some Belarusians might be “fed up” with his rule but he was adamant that he wouldn’t leave office, according to the journalists..
He asserted that he was the only person who could “defend” Belarus.
Alexander Lukashenko calls Vladimir Putin “big brother” in this interview and he’s increasingly dependent on Russia for support. But his comments reveal a confidence that Moscow needs him, too.
“You know what we agreed with the Russian establishment and leadership?” he asked the panel of Russian state TV reporters on the sofas before him. “That if Belarus breaks, Russia will be next.”
Back me up, Mr Lukashenko seemed to be saying to Moscow, and your own people won’t get any bad ideas about ousting a long-standing leader through popular protests.
As usual, he claimed the unrest in Belarus was fomented by hostile outside forces, mainly America, via the internet.
But with opposition to his rule strong and persistent, Mr Lukashenko is now heavily reliant on his security forces.
So he had a message for them too. If I go, he argued, the riot police would be “slaughtered, torn to pieces. And what have they done wrong?”
Mr Lukashenko has twice appeared brandishing a gun during mass protests against his rule, and he told the reporters it was meant to show he had not fled.
He has accused Western powers of interference and is expected to visit Moscow “in the coming days” amid claims by Lithuania that he is planning deeper integration with Russia.
What has happened to the three women in opposition?
Of the three women who joined forces in the election against the Belarusian leader, only Maria Kolesnikova is still in the country.
She was initially the campaign manager for presidential candidate Viktor Barbaryko but after his arrest in June she decided to work with Veronika Tsepkalo and Svetlana Tikhanovskaya,
Ms Tikhanovskaya only decided to run in the election after her husband was arrested and barred from standing. She was forced to leave Belarus for Lithuania the day after the vote, having been detained for several hours.
Ms Tsepkalo has travelled to Poland with her husband, Valery, and children. Mr Tsepkalo, the former Belarusian ambassador to the US, was also barred from standing against President Lukashenko.
Another female activist, Olga Kovalkova, announced on Saturday she had fled to Poland amid threats of imprisonment.
“I’m the only one of the three of us who is still here,” Ms Kolesnikova told BBC Russian in an interview last month. “To understand exactly what’s going on, you really have to be here.”
Ms Kolesnikova described the recent demonstrations as “not a struggle for power” but “a struggle for human dignity and self-respect”. She said she and her team had decided against using bodyguards.
“No number of guards would be of any use if a bus full of riot police stopped us,” she said. “We all know what a police state is capable of.”