MOSCOW (AP) — A Moscow court on Monday ordered the wife of Russian opposition leader Alexei Navalny to pay a fine of 20,000 rubles ($265) for violating protest regulations after she attended a demonstration in the Russian capital to demand his release.

Tens of thousands protested across Russia’s 11 time zones on Sunday, chanting slogans against Russian President Vladimir Putin and demanding that authorities free Navalny, who was jailed last month and faces a prison term. Over 5,400 protesters were detained by authorities, one group said.

While Russia's state-run media dismissed the demonstrations as small and claimed that they showed the opposition's failure, Navalny’s team said the turnout on Sunday demonstrated “overwhelming nationwide support” for the Kremlin's fiercest critic.

Navalny's allies have called for another demonstration in Moscow on Tuesday, when a court is scheduled to hear the authorities' motion to send him to prison for up to 3 1/2 years.

His wife, Yulia Navalnaya, joined a protest in Moscow on Sunday that took place despite unprecedented security measures that city authorities took ahead of the rally. She was quickly detained and charged with participating in an unauthorized rally. A court on Monday ordered Navalnaya to pay a fine, her lawyer Svetlana Davydova told the Interfax news agency. Davydova said the defense plans to appeal the ruling.

In the largest outpouring of discontent Russia had seen in years, mass protests engulfed dozens of Russian cities for the second weekend in a row despite efforts by Russian authorities to stifle the unrest triggered by the jailing of 44-year-old Navalny, the Putin's most well-known foe.

Navalny was arrested Jan. 17 upon his return from Germany, where he spent five months recovering from nerve-agent poisoning that he blames on the Kremlin. Russian authorities have rejected the accusations. He faces a prison term for alleged probation violations from a 2014 money-laundering conviction which has been widely seen as politically motivated.

After his arrest, Navalny's team released a two-hour YouTube video about an opulent Black Sea residence purportedly built for Putin. The video has been viewed over 100 million times, further stoking Russians' discontent amid an economic downturn.

The rallies following Navalny's arrest appear to have rattled the Kremlin. In an effort to quell the protests, the authorities have jailed Navalny’s associates and activists across the country. His brother Oleg, top ally Lyubov Sobol and three other people were put under a two-month house arrest and face criminal charges.

A total of 40 criminal probes have been opened in 18 Russian regions in connection to the protests, said Pavel Chikov, head of the human rights organization Agora.

Russian authorities cracked down hard on the demonstrators Sunday, detaining over 5,400 people, according to OVD-Info, a legal aid group that monitors arrests at protests. The group said that was the highest number in its nine-year history of keeping records in the Putin era.

OVD-Info said at least 51 protesters were beaten by police officers while being detained. Footage of the protests showed riot police beating people with truncheons and throwing them on the ground. Media reported some protesters were hit with Tasers.

When asked Monday about the mass detentions, Kremlin spokesman Dmitry Peskov noted that the protest was “unlawful” and charged that “there was a fairly large number of hooligans, provocateurs with more or less aggressive behavior towards law enforcement officers."

“In response to provocations, the police act harshly and within the law,” Peskov said.

Russian state media also highlighted “aggressive actions” of the protesters in their coverage of Sunday's demonstrations, which reports said were joined by “times fewer” people than on Jan. 23. Many reports underscored “polite” actions by police officers, and state TV channel Russia 1 even aired video statements of people thanking law enforcement officers in the wake of the rallies.