MOSCOW — Maria Kolesnikova, the last prominent protest leader in Belarus still at large, vanished on Monday and local news media outlets reported that she had been grabbed off the street by masked kidnappers in the center of the East European nation’s capital, bundled into a dark minivan and driven away at speed.
The abduction of Ms. Kolesnikova, the latest in a series of disappearances apparently engineered by Belarus’s security agencies, followed large protests on Sunday in Minsk, the capital, and towns across the country. It seemed to reflect a shift in strategy from the initial frenzy of police violence against protesters to picking off opposition leaders one by one and sending them out of the country.
Linas Linkevicius, the foreign minister of neighboring Lithuania, said Ms. Kolesnikova had been the victim of a “kidnapping,” deploring in a Twitter post that “Stalinist N.K.V.D. methods are being applied in 21st century Europe.”
The N.K.V.D. was the precursor of the K.G.B., a name still proudly embraced by the main security agency in Belarus, a former Soviet republic that has often been described as “Europe’s last dictatorship.”
At a news conference on Monday in Warsaw, the capital of neighboring Poland, exiled members of a coordination council set up last month in Minsk by opponents of President Aleksandr G. Lukashenko said that Ms. Kolesnikova, a member of the council’s presidium, had disappeared without a trace off the street in Minsk in the morning.
Olga Kovalkova, a member of the council who was herself arrested two weeks ago in Minsk and then forced to leave Belarus for Poland over the weekend, said that Ms. Kolesnikova had been “kidnapped in central Minsk” by “unknown people.”
“Her whereabouts are unknown,” Mrs. Kovalkova added.
Tut, a Belarusian news site sympathetic to the opposition, quoted a witness to Ms. Kolesnikova’s abduction as saying that the opposition leader had been walking near the National Art Museum in Minsk when she was confronted by masked people in civilian clothes and pushed into a waiting van marked with the word “Communication.”
Ms. Kolesnikova first gained prominence as an election campaign manager for Viktor Babariko, a prominent Belarusian banker who had planned to run against Mr. Lukashenko in August. Before he could challenge the president, however, he was arrested on what were widely seen as trumped up financial charges. He is still in jail.
After using often savage violence against protesters but still failing last month to tamp down widespread anger over the Aug. 9 election, in which the president claimed an implausible landslide victory, Mr. Lukashenko’s security apparatus seems to have adopted a subtler tactic of targeted attacks on protest leaders.
Mr. Linkevicius accused Mr. Lukashenko, whom he described as Belarus’s “outgoing leadership,” of trying to “eliminate” his most outspoken foes “one by one.”
Ms. Kolesnikova’s disappearance removes 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.
Maksim Znak, a member of the opposition council’s presidium, said on Monday that the body coordinating protests would have to rethink its approach because all but two members of its leadership had vanished into jail or been pressured into leaving the country. The two remaining members, he said, are himself and the Nobel-prize winning writer, Svetlana Alexievich, who has been called in for questioning but so far avoided detention.
Instead of simply throwing his most prominent opponents in jail, which would risk inflaming public anger, Mr. Lukashenko has started pressuring them to flee to either Lithuania or Poland, both members of NATO, and then casting them as traitors working with Western powers to undermine both Belarus and Russia.
Mr. Lukashenko, who has ruled Belarus since 1994, has repeatedly presented weeks of unrest as a NATO plot and used this to rally support for his government from President Vladimir V. Putin of Russia. When the protests started nearly a month ago, Mr. Putin offered only lukewarm backing but, complaining of Western meddling, he announced late last month that he had formed a reserve force of Russian security officers ready for action in Belarus if “the situation gets out of control.”
By stripping the opposition of its leadership, Mr. Lukashenko apparently hopes to gradually stall the protests’ momentum, allowing his security forces to frighten those who continue protesting with the threat of mass arrests. The Interior Ministry said on Monday that nearly 700 protesters had been arrested on Sunday.
On Saturday, Ms. Kovalkova, an ally of Ms. Tikhanovskaya, became the latest opponent of Mr. Lukashenko to be forced to leave Belarus. Arrested two weeks ago in Minsk, she suddenly reappeared in Poland. She told the news conference in Warsaw that K.G.B. officers in Minsk had offered a stark choice: either stay in prison indefinitely or leave the country.
She said Belarusian security officials put her head in a hood, bundled her into a car that drove across the country and then dumped her on the border with Poland. The Belarusian Interior Ministry told a Russian news agency that she had been released for medical reasons.
Ivan Nechepurenko contributed reporting