As a few thousand people marched in the southern Russian city of Rostov-na-Donu last month, local schoolteacher Alexander Ryabchuk posted videos of the protest on his Instagram page.

The following week, the headmistresses of both schools where Ryabchuk taught called him into their offices, warned him that “very serious people” had complained about his social media activity, and fired him on the spot after he refused to delete the posts.

One school warned him about the complaints, and at the other a “serious” person turned up to pressure him. Within days, police raided Ryabchuk’s apartment and arrested him; a court jailed him for five days, ostensibly for blocking traffic during the protest.

“They obviously wanted to scare me and take away my livelihood,” Ryabchuk, 31, told the Financial Times. “But I think they’re more scared than I am. I only obeyed the law and my conscience.”

Ryabchuk’s ordeal is a sign of jitters in the Kremlin about nationwide protests sparked by the arrest of Alexei Navalny, president Vladimir Putin’s most prominent opponent.

Police arrested more than 10,000 people at protests on consecutive weekends in January, according to independent monitor OVD-Info, including nearly 1,500 on the day Navalny was sentenced to three-and-a-half years in prison last week. Nearly 1,300 of them were sentenced to brief jail terms in Moscow and St Petersburg alone, while more than 90 face more serious criminal charges, according to the interior ministry. At least 140 protesters were beaten by police according to Apologia Protests, a public defenders’ association that represents some of the demonstrators.

The crackdown has shocked many, even in a country harbouring few illusions about the Kremlin’s shrinking tolerance for dissent. Riot police have shut down large parts of central Moscow and St Petersburg, viciously beaten protesters with batons, and detained journalists.

Though several of those jailed alleged to the FT that police falsified charges against them, the Kremlin has accused western countries of organising the protests. “There are no repressions,” Dmitry Peskov, Putin’s spokesman, told reporters last week. “There are measures taken by the police against lawbreakers and participants in illegal protests.”

For now, the harsh treatment of protesters appears to have had the desired effect. Leonid Volkov, Navalny’s chief of staff, admitted this week that “peaceful street protests have been put down through unprecedented police violence”.

Volkov put off fresh protests until the spring, then called on Russians to wave their phone flashlights outside their front doors on Sunday evening, so that “riot police can’t stop it and everyone can come”. Several of Navalny’s other top aides also face years in prison on charges of violating pandemic health rules.

Though sympathy for the protests is widespread, many Russians nevertheless oppose the rallies. According to a poll released by the independent Levada Center on Wednesday, 39 per cent of those surveyed said they disapproved of the protests, with only 22 per cent approving. Though 43 per cent of respondents said protesters were motivated by “pent-up anger at the situation in the country”, 28 per cent said the protesters had probably been paid to attend.

State TV portrays Navalny as a CIA agent bent on destroying Russia, while official pressure on independent journalists has been considerable. More than 80 reporters were detained in Moscow on January 31 alone, according to a journalists’ trade union.

In Vladivostok on the Pacific coast, riot police raided independent reporter Gennady Shulga’s apartment early on Saturday morning and filmed a mock interrogation — even though he is only a witness in a protest-related case. The video then mysteriously appeared online, a move Shulga said he felt was aimed at intimidating him from covering future protests.

The crackdown, however, does little to address the underlying discontent that fuelled the protests in the first place, said Alexander Tevdoy-Bourmouli, a political-science professor at Moscow’s MGIMO university. “There’s a logic to it, but it’s not very rational, because instead of solving the problems, it drives them into a corner, where they’ll blow up into a more serious crisis,” he said.

Tevdoy-Bourmouli, a foreign policy specialist, witnessed the Kremlin’s reaction first-hand in January when he and his daughter were arrested after they exited a metro station in central Moscow. Police then claimed in court that he held up traffic and chanted slogans. Though Tevdoy-Bourmouli insisted he had done no such thing and his lawyer attempted to present evidence of his type 1 diabetes — which, under Russian law, makes him ineligible for short-term detention — a judge jailed him for 12 days.

“It’s no secret. They rubber-stamp hundreds of thousands of documents and have policemen who didn’t even do the arrest sign them,” Tevdoy-Bourmourli said.

As the record arrests pushed Moscow’s jails to breaking point, protesters spent several sleepless nights in crowded police station cells. “There were portraits of Putin everywhere . . . [B]being surrounded by him was really creepy,” said Maryam Salarzai, 23.

She found herself among hundreds of protesters sent to a detention centre for migrants in Sakharovo, a suburb of northern Moscow. The facility was so overwhelmed by the sudden influx of detainees that as many as 28 were held at a time in cells meant for four before guards moved them. Though Peskov acknowledged the overcrowding, he blamed the detainees, saying that “this situation wasn’t provoked by law enforcement, but by participation in unsanctioned protest”.

Some of those who had been held at Sakharovo told the FT they were forced to relieve themselves in a hole in the floor in full sight of the other inmates, denied regular access to water, and given inedible food. Others complained guards refused to pass on packages sent by friends and relatives.

To keep their spirits up, detainees chanted “Putin is a thief!” during exercise hours, sang protest song, and posed for a video in the detention centre’s courtyard. Later, investigators threatened some prisoners with criminal prosecution for insulting government officials, according to OVD-Info.

The authorities have already vowed to suppress any protests on Sunday. But Ryabchuk, who was released from jail on Tuesday, remains unbowed. “I teach free democratic ideals, the rule of law, and parliamentarianism . . . and I have to show examples from outside my country,” he said. “I realised I’ve already said so much about it — now it’s time to do something.”