MOSCOW — Maria Kolesnikova, a prominent opposition leader in Belarus who vanished on Monday in what her supporters said was a kidnapping by security agents, reappeared overnight at her country’s southern border with Ukraine.
But an elaborate operation aimed at forcing her to leave Belarus came unstuck, according to opposition activists who were at the border with Ms. Kolesnikova when she destroyed her passport to make it impossible for Ukraine to admit her.
At a news conference in Kyiv, the capital of Ukraine, on Tuesday evening, two Belarusian activists, Anton Rodnenkov and Ivan Kravtsov, told how they had been seized in Minsk, the capital of Belarus, on Monday and taken to the border with Ukraine, along with Ms. Kolesnikova, by masked security agents who warned that if they did not leave the country they would be jailed indefinitely.
After passing through a Belarusian border checkpoint, they said, Ms. Kolesnikova grabbed her passport and started shouting that she was not going anywhere. She tore the passport into small pieces and threw them out of the window.
Mr. Rodnekov and Mr. Kravtsov continued onto Ukraine without her. “She climbed out of the car and started walking back toward the Belarus border,” Mr. Kravtsov said. “She is very brave and dedicated to what she is doing.”
Ukraine’s deputy minister for internal affairs, Anton Gerashchenko, confirmed that the authorities in Belarus had planned a “forced expulsion” of Ms. Kolesnikova, but said the plans were not completed “because this brave woman took action to prevent her movement across the border.” He added that she “remained on the territory of the Republic of Belarus.”
The whereabouts of Ms. Kolesnikova had been the focus of intense speculation since she disappeared from a street in Minsk early on Monday. A witness quoted by local media said Ms. Kolesnikova, a leading member of a coordinating council set up by opponents of Belarus’ embattled president, Aleksandr G. Lukashenko, had been grabbed by masked abductors and bundled into a van.
Her supporters denounced the apparent abduction as the work of Mr. Lukashenko’s security forces and a sign that the authorities had shifted their strategy in response to nearly a month of protests over a disputed election on Aug 9.
Instead of attacking protesters with often savage violence, the security apparatus now seems to be trying to demobilize the opposition movement by picking off its leaders one by one and sending them out of the country.
Mr. Lukashenko, in an interview with Russian journalists, gave his own account of events at the border, claiming that Ms. Kolesnikova had tried to flee Belarus illegally in a car with two fellow activists, but had been thrown out of the vehicle on the way to Ukraine. He said that Belarusian border officers then arrested her.
Dressed in business attire and unarmed, unlike in a previous public appearance when he swaggered outside the presidential palace wearing a black track suit and waving an assault rifle, Mr. Lukashenko used the interview to try and project an image of calm confidence.
He conceded that, after 26 years in power, he had “perhaps overstayed a bit,” but made clear that he had no intention of stepping down, claiming that his supporters would be “slaughtered” if he quit. “I’m not going to simply throw it all away,” he said.
He also repeated what has become his favorite pitch for Russian support, asserting that Belarus could not survive without him and that “if Belarus collapses today, Russia will be next.”
Belta, the official Belarus news agency, reported that a car carrying Ms. Kolesnikova and her two opposition colleagues had arrived near the border around 4 a.m. on Tuesday but that Ms. Kolesnikova had been pushed from the vehicle as it sped off toward the Ukrainian border post.
This bizarre version of events cast what seems to have been a forced departure gone awry as an unsuccessful escape attempt. Belta claimed that the car carrying Ms. Kolesnikova had “posed a threat to the life of a border guard.”
Ms. Kolesnikova had been the last member still active inside Belarus of a trio of female activists behind a groundswell of opposition to Mr. Lukashenko. The other two, Svetlana Tikhanovskaya, Mr. Lukashenko’s main challenger in the disputed election, and Veronika Tsepkalo, the wife of a would-be candidate who fled before polling day, both left Belarus to avoid arrest soon after Mr. Lukashenko claimed re-election.
Since then, a number of other opposition activists have also left Belarus under duress, threatened with long jail terms and trouble for their families if they stayed.
This program of expulsions seems to have begun at the advice of security officials from Moscow, who have become more involved in advising Mr. Lukashenko in recent weeks and have urged him to stop inflaming the anger of protesters with beatings and mass arrests.
President Vladimir V. Putin of Russia, who has never warmed to Mr. Lukashenko but still sees him as an important bulwark against the West, announced at the end of August that he had formed a reserve force of Russian security officers to assist Belarus if “the situation gets out of control.”
In another sign of close collaboration between the two countries, Belarus announced on Tuesday that it would hold military exercises later this week with troops from Russia and Serbia. The exercises, called Slavic Brotherhood 2020, underscore an important propaganda point for Mr. Lukashenko, suggesting that he is not alone in his struggle for political survival but a sentinel for broader Slavic interests against the West.
Maria Varenikova contributed reporting from Kyiv.