The recent high school graduate selected her wardrobe carefully as she headed off to a summer folk festival.

She dressed all in white, as is customary for the event, and wore a large flower wreath in her golden hair. But when it came to choosing a sash for her skirt, she grabbed a brown leather band, avoiding the color red.

In Belarus, red and white are the colors of the protest movement against the country’s authoritarian leader, Aleksandr G. Lukashenko. And even the smallest sign of protest can land a person in jail. “I worry about attracting the wrong kind of attention from the authorities,” said the young woman, who spoke on the condition that her name not be used so she would not draw scrutiny.

After claiming victory in a widely disputed presidential election three years ago — and violently crushing the outraged protests that followed — Mr. Lukashenko has ushered in a chilling era of repression.

He is moving ever closer to his patron, President Vladimir V. Putin of Russia, positioning himself as an invaluable military ally to Russia in its war against Ukraine, but also cracking down on dissent in a way that is invisible to much of the world but rivals that of Mr. Putin’s punitive regime.

Belarusian security forces are rounding up opposition figures, journalists, lawyers and even people committing offenses like commenting on social media memes or insulting Mr. Lukashenko in private conversations with acquaintances that are overheard and reported.

In particular, activists and rights groups say, the country’s security forces are intent on finding and punishing the people who participated in the 2020 protests. Belarusians are getting arrested for wearing red and white, sporting a tattoo of a raised fist — also a symbol of the protest movement — or for just being seen in three-year-old photographs of the anti-government demonstrations.

“In the last three years, we went from a soft autocracy to neo-totalitarianism,” said Igor Ilyash, a journalist who opposes Mr. Lukashenko’s rule. “They are criminalizing the past.”

Belarusians interviewed by The New York Times over three days this month echoed that sentiment, expressing fear that even a slight perceived infraction related to the revolution could bring prison time.

The crackdown has made people much more cautious about overtly showing their anger at the government, said Mr. Ilyash. That, in turn, has prompted the authorities to focus on participation in old protests in an attempt to intimidate and stifle dissent.

Scrutiny of Mr. Lukashenko’s repressive reign has increased since Russia’s invasion of Ukraine last year, and in particular in recent months.

Belarus let the Kremlin invade Ukraine from its territory last year. In March, Russia announced it would station tactical nuclear weapons on Belarusian territory. Video evidence suggests Belarus is now housing forces from Russia’s Wagner paramilitary group, and on Thursday, the government said Wagner forces were training special Belarusian operations units only a few miles from the border with Poland.

The security crackdown has thinned the ranks of lawyers: More than 500 have been stripped of their law licenses or left the profession or the country.

And Belarus has become particularly perilous for journalists. There are now 36 in jail, according to the Belarusian Association of Journalists, after the arrest on Monday of Ihar Karnei, 55. He has written for the U.S.-funded Radio Free Europe/Radio Liberty, which Belarus has banned as an “extremist” organization. People can be sentenced to up to seven years in prison for just sharing its content.

According to Viasna, a human rights group that shared the Nobel Peace Prize last year, security forces raided Mr. Karnei’s home and seized his electronic devices. He is in Belarus’s notorious Okrestina detention center, the group said, and neither his family nor his lawyers have had access to him.

Belarus has criminalized most independent news outlets and the journalists’ association as “extremist,” which makes following them on social media a crime.

Mr. Ilyash’s wife, the award-winning journalist Katsiaryna Andreyeva, was sentenced to eight years in prison in two separate cases and now labors in a penal colony as a seamstress, earning less than $4 a month, her husband said.

In the prison, she is forced to wear a yellow badge on her chest identifying her as a political prisoner. When she is released in 2028, if the same government is still in power, she will still be considered an “extremist” and barred from certain activities, including journalism.

Mr. Ilyash himself spent 25 days in prison, and with one criminal case against him still open, he is barred from leaving the country. He does not leave his apartment without a small backpack that contains the essentials for prison, in case he is detained: a toothbrush, toothpaste, spare underwear and socks.

Activists and opposition figures are also being targeted. This month, the artist Ales Pushkin died in a penal colony at age 57. He is believed to be the third political prisoner to die in Belarusian custody since the protests began in 2020.

Several of the country’s best-known political prisoners, like the leading opposition figure Maria Kolesnikova, have neither been seen by their family members or lawyers, nor permitted to write letters, meaning they have been out of touch for months.

Viasna, the rights group, has identified almost 1,500 political prisoners in Belarus today, and a further 1,900 people convicted in what the group calls “politically motivated criminal trials.”

“The security services are still watching people’s videos, and scouring social media and photos of the protests all these years later,” said Evgeniia Babayeva, a Viasna staff member who catalogs politically motivated detentions in Belarus from exile in Lithuania.

Ms. Babayeva was arrested in July 2021, on the same day as the group’s founder, Ales Bialiatski, along with a handful of other colleagues. She was released only because she signed an agreement to collaborate with the security services, but she said she fled Belarus the same day.

In March, Mr. Bialiatski was sentenced to 10 years in prison for “cash smuggling” and “financing actions and groups that grossly violated public order,” charges widely viewed by watchdog groups as spurious and intended to discredit the organization.

On the surface, visitors to the country’s capital would have to look closely to see any signs that the protests in 2020 happened at all. Minsk, which takes pride in its cleanliness, is tidy, with a modern city center. Billboards trumpet 2023 as the “year of peace and creation,” and the roadside public gardens are manicured in national Belarusian motifs.

But residents say a more ominous sensibility hangs over the city and the country. Cameras with facial recognition ability watch over public spaces and residential elevators, keeping tabs on ordinary Belarusians carrying out day-to-day activities.

One evening in June, a Minsk resident was out for a walk when she was approached by the police, who reprimanded her for a simple administrative violation, less serious than jaywalking.

The officer searched her name in the police database, turning up evidence of previous detention for participation in the 2020 protests. Police officers soon drew up an accusation that she had cursed in their station — which she denies — and she was put into the Okrestina detention center for 10 days on a “hooliganism” charge.

She shared a small cell with 12 other women, she said. There were no mattresses or pillows, and the light was on 24 hours a day. Though everyone became sick — she contracted a bad case of Covid — they had to share toothbrushes. There were no showers, and if a woman got her period, she was given cotton balls rather than pads or tampons.

(The woman’s name and her offense are being withheld at her request because the information could identify her and draw retribution. Her identity was confirmed by The Times, and friends confirmed that she had given similar accounts to them.)

The repressive environment is stifling people and prompting many to leave. The high school graduate who went to the celebration of the summer solstice and the Belarusian poet Yan Kupala said she had attended because of a dearth of public events since 2020.

“There is nowhere for us to go anymore,” she said, complaining that control was so tight that even traditional songs had been approved in advance by the authorities. She said most good musicians have been named “extremists” and left the country.

The girl said she planned to follow them, hoping to continue her studies in Cyprus or Austria. At least half of her classmates had already left Belarus.

Another festivalgoer, Vadim, 37, said he had the impression that at least half of his friends had spent time in prison because of their political views.

He said his wife had already emigrated, and he was contemplating joining her.

“The war was a trigger for many people to leave,” he said.

“Before, we thought this situation would eventually end,” Vadim said, “but once the war started, we knew it would only get worse.”