MOSCOW (AP) — Opposition leader Alexei Navalny denounced a Moscow court hearing Tuesday on whether he should be sent to prison for years, calling it a vain attempt by the Kremlin to scare millions of Russians into submission.

The 44-year-old Navalny, an anti-corruption investigator who is the most prominent critic of President Vladimir Putin, was arrested Jan. 17 upon returning from Germany, where he spent five months recovering from a nerve-agent poisoning that he blames on the Kremlin. Russian authorities deny the charge and claim, despite tests by several European labs, that they have no proof he was poisoned.

Speaking from a glass cage in the courtroom, Navalny attributed his arrest to Putin’s “fear and hatred," saying the Russian leader will go down in history as a “poisoner.”

“I have deeply offended him simply by surviving the assassination attempt that he ordered,” he said.

“The aim of that hearing is to scare a great number of people,” Navalny said. “You can't jail the entire country."

Russia’s penitentiary service alleges that Navalny violated the probation conditions of his suspended sentence from a 2014 money laundering conviction that he has rejected as politically motivated. It has asked the Simonovsky District Court to turn his 3 1/2-year suspended sentence into one that he must serve in prison.

Navalny emphasized that the European Court of Human Rights has ruled that his 2014 conviction was unlawful and Russia paid him compensation in line with the ruling.

Navalny and his lawyers have argued that while he was recovering in Germany from the poisoning, he couldn't register with Russian authorities in person as required by his probation. Navalny also insisted that his due process rights were crudely violated during his arrest and described his jailing as a travesty of justice.

“I came back to Moscow after I completed the course of treatment,” Navalny said at Tuesday's hearing. “What else could I have done?”

Navalny's jailing has triggered massive protests across Russia for the past two weekends, with tens of thousands taking to the streets to demand his release and chant slogans against Putin. Police detained over 5,750 people Sunday, including more than 1,900 in Moscow, the biggest number the nation has seen since Soviet times. Most were released after being handed a court summons, and they face fines or jail terms of seven to 15 days. Several people faced criminal charges over alleged violence against police.

“I am fighting and will keep doing it even though I am now in the hands of people who love to put chemical weapons everywhere and no one would give three kopecks for my life,” Navalny said.

Navalny's team called for another demonstration Tuesday outside the Moscow courthouse, but police were out in force, cordoning off the nearby streets and making random arrests. More than 320 people were detained, according to the OVD-Info group that monitors arrests.

Some Navalny supporters still managed to approach the building. A young woman climbed a large pile of snow across the street from the courthouse and held up a poster saying “Freedom to Navalny.” Less than a minute later, a police officer took her away.

In court, Navalny thanked protesters for their courage and urged other Russians not to fear repression.

“Millions can't be jailed,” he said. “You have stolen people's future and you are now trying to scare them. I'm urging all not to be afraid."

After his arrest, Navalny’s team released a two-hour YouTube video featuring an opulent Black Sea residence allegedly built for Putin. The video has been viewed over 100 million times, fueling discontent as ordinary Russians struggle with an economic downturn, the coronavirus pandemic and widespread corruption during Putin's years in office.

Putin insisted last week that neither he nor his relatives own any of the properties mentioned in the video, and his longtime confidant, construction magnate Arkady Rotenberg, claimed that he owns it.

As part of efforts to squelch the protests, the authorities have targeted Navalny’s associates and activists across the country. His brother Oleg, top ally Lyubov Sobol and several others were put under house arrest for two months and face criminal charges of violating coronavirus restrictions.

The jailing of Navalny and the crackdown on protests have stoked international outrage, with Western officials calling for his release and condemning the arrests of demonstrators.

Visiting Moscow on Tuesday, Swedish Foreign Minister Ann Linde, the current chair of the Organization for Security and Cooperation in Europe, urged Russia to release Navalny and condemned the crackdown on protests.

EU foreign policy chief Josep Borrell, who will visit Moscow later this week, has criticized the detentions and the disproportionate use of force against protesters, emphasizing that Russia must comply with its international commitments on human rights.

Russia has dismissed U.S. and EU criticism as meddling in its domestic affairs and said Navalny's current situation is a procedural matter for the court, not an issue for the government.

More than a dozen Western diplomats attended the hearing, and Russian Foreign Ministry spokeswoman Maria Zakharova said their presence was part of efforts by the West to contain Russia, adding that it could be an attempt to exert “psychological pressure” on the judge.

Kremlin spokesman Dmitry Peskov said Russia is ready for dialogue about Navalny, but sternly warned that it wouldn't take Western criticism into account.

“We are ready to patiently explain everything, but we aren't going to react to mentor-style statements or take them into account,” Peskov said in a conference call with reporters.