Russian opposition leader Alexei Navalny faces a court hearing that could end with him being jailed for years.

The 44-year-old, an anti-corruption investigator who is the most prominent critic of President Vladimir Putin, was arrested on January 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.

Russia’s penitentiary service alleges that Mr 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 in Moscow to turn his three-and-a-half-year suspended sentence into one that he must serve in prison.

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

Mr Navalny’s jailing has triggered massive protests across Russia over the past two weekends, in which tens of thousands took to the streets to demand his release, chanting slogans against Mr Putin. Police detained more than 5,750 people during Sunday’s rallies, including more than 1,900 in Moscow, the biggest number the nation has seen since Soviet times. Some were beaten.

Most were released after being handed court summons and face fines or jail terms of 7-15 days. Several people faced criminal charges over alleged violence against police.

Mr Navalny’s team has called for another demonstration on Tuesday outside the Moscow court building. Police were deployed in force near the court building and cordoned off nearby streets, making random detentions.

After his arrest, Mr Navalny’s team released a two-hour YouTube video featuring an opulent Black Sea residence allegedly built for Mr Putin. The video has been viewed more than 100 million times, fuelling discontent as ordinary Russians struggle with an economic downturn and the coronavirus pandemic.

Mr Putin insisted last week that neither he nor his relatives own any of the properties mentioned in the video.