Russia is planning early next week to charge Alexei Navalny, an anti-corruption crusader and a leader of the opposition, in a probe over losses at a state-owned firm, his lawyer said yesterday.

The probe represents one of the most serious legal challenges yet for Mr Navalny, 36, a charismatic lawyer who has twice spent short stints in jail for his role in protests against President Vladimir Putin.

“Alexei has been ordered to appear Monday at the Investigative Committee (in Moscow) to face charges over the so-called KirovLes case,” defence lawyer Vadim Kobzev said.

Mr Kobzev said he did not know whether Mr Navalny would be arrested but added he could face between two and five years in prison under the charges of causing damage to assets.

Investigators earlier this month re-opened a two-year-old probe against Mr Navalny after Russia’s top investigator Alexander Bastrykin dressed down his subordinates in the Kirov region for closing it earlier this year.

“You had a criminal probe against this person and you closed it on the sly,” government newspaper Rossiiskaya Gazeta quoted Mr Bastrykin as saying earlier this month. “There won’t be mercy for such things.”

According to investigators, forestry firm KirovLes company sustained losses of over one million rubles ($30,900) between April and August 2009 due to the actions of Mr Navalny, who at the time was an adviser to the Kirov region’s governor. Mr Navalny has denied the charges.

Known for his rousing rhetoric and knack for catchphrases, Mr Navalny has emerged as the star of the protest movement against Mr Putin’s decade-long rule and one of its biggest hopes as a serious challenge to the Russian strongman.

Over the past months he tirelessly encouraged Russians to fight for their rights and published a number of reports exposing corruption in the government and state companies. In April, Time magazine named him among the world’s 100 most influential people.

On Thursday, Mr Navalny in an apparent counter-attack on Mr Bastrykin, published documents alleging that Mr Bastrykin had until 2009 a long-term residence permit in the Czech Republic as well as undeclared business interests.