MOSCOW: Russian authorities charged Alexei Navalny, one of President Vladimir Putin’s fiercest critics, with theft Tuesday, threatening a 10-year prison sentence as the Kremlin ramps up a crackdown on dissent.

Navalny rejected the charges as “weird” and baseless. Navalny, a 36-year-old anti-corruption crusader, has played a key role in rallying Russia’s young Internet generation against Putin’s rule. Over the winter, the lawyer spearheaded a series of rallies in Moscow that drew up to 100,000 people to the streets ahead of the March vote that handed Putin a third presidential term.

The State Investigative Committee said Tuesday that it suspects Navalny of organizing a scheme to steal assets from a state timber company totaling 16 million rubles [about $500,000]. He was ordered not to leave Moscow as the committee pursues an investigation against him.

In Russia, authorities file initial charges to open a criminal probe, long before reaching the trial stage. In any case, Navalny insisted to reporters, “The charges are absolutely absurd.”

Since Putin’s re-election, the government has struck back at the opposition, arresting some activists and using legislation to try curbing its activities.

Parliament, controlled by Putin loyalists, passed a bill that raised fines 150-fold for people taking part in unsanctioned protests. Another bill passed this month requires non-governmental groups receiving funding from abroad and engaging in political activity to register as foreign agents.

In one example of the tougher line on dissent, three Russian feminist rockers have gone on trial for performing a “punk prayer” against Putin in Moscow’s main cathedral. They face up to seven years in prison, and human rights groups have condemned the trial, calling them prisoners of conscience.

The probe against Navalny focuses on events dating to 2009 when he served as an adviser to a provincial governor in the Kirov region. Investigators allege that he colluded with the head of a state timber company and a trader to rob it. A previous probe into similar allegations was closed earlier this year for lack of evidence.

Investigative Committee chief Alexander Bastrykin recently chided a local investigator for closing that case. Under the renewed probe, investigators reworded the charges, to carry a heavier punishment compared to those dropped.

“There is no motive, there is no self-interest, the amount of damage is taken out of the blue,” Navalny said on his blog about the new charges. “The Investigative Committee has no shame.”

Navalny, who has more than 270,000 followers on Twitter and owes much of his popularity to his investigations of rampant official corruption, has in recent days targeted Bastrykin, claiming that the chief investigator has covertly obtained a Czech residency permit and bought an apartment in Prague.

Bastrykin defended himself in an interview with the daily Izvestia, admitting that he bought the apartment but denying having the residency permit.

Swedish Foreign Minister Carl Bildt expressed concern over the new charges against Navalny.

“We should be concerned with attempts in Russia to silence fierce opposition activist Alexei Navalny,” he tweeted.