Russia on Tuesday charged popular protest leader Alexei Navalny with embezzlement, reviving a case that could land one of President Vladimir Putin's most vocal critics behind bars for 10 years. The Investigative Committee said Navalny would also be barred from leaving Moscow during the probe into his role as an unofficial adviser in a small deal struck by regional officials in 2009. The charismatic 36-year-old, a corporate lawyer by profession, looked pale as he came out from closed hearings during which the charges against him were expanded substantially to include some of Russia's gravest business crimes. "Something absolutely absurd and very strange has happened because they have completely changed the story behind the charge," the prominent anti-corruption blogger told reporters waiting outside the gates. "I cannot imagine how the investigators can prove this. But probably they will prove it." Navalny seems likely to be jailed for a substantial term, his lawyer said. "It all looks as if Navalny is going to get a jail term of seven years or so," lawyer Vadim Kobzev told the RAPSI legal news agency. Hours after the charge, Putin stressed that Russia does not use its judicial system to incarcerate activists. "I can say firmly that there is no such tool nor desire in the state's political arsenal -- to suppress anyone with prison for their human rights activity," he said at a youth forum, without mentioning Navalny. Navalny became a cult figure in Russia's growing Internet community with his investigations into state corruption before helping to spearhead the wave of protests that rocked the Kremlin in the winter months. He has emerged as one of the most prominent leaders of a splintered protest movement that has faced a crackdown from authorities since Putin's disputed third presidential term began in May. The charges are likely to unite the opposition around Navalny, said liberal opposition politician Boris Nemtsov. "After Navalny was handed 100 percent fabricated charges today, the situation became clearer. Alexei has every chance of heading the opposition," Nemtsov wrote on Facebook. The charges relate to a case that investigators had dropped in the past. But the powerful Investigative Committee chief Alexander Bastrykin this month personally demanded the case be reopened. Investigators had originally accused Navalny of causing a loss of 1.3 million rubles ($40,000) to the budget of the Kirov region by advising a local state-owned timber firm to sign a deal with another small company in 2009-2010. The charges released Tuesday hiked the alleged loss to the budget to 16 million rubles ($500,000) and accused Navalny of acting in cahoots with the private timber firm. Navalny compared the legal grounds to the case of former Yukos oil chief Mikhail Khodorkovsky, convicted of fraud and then tax evasion in widely criticised trials after he openly opposed Putin. "All those jokes about how Khodorkovsky stole all the oil and Navalny all the timber, that is basically what has happened," Navalny said. The case appears to be an attempt to give Navalny a taste of his own medicine after he exposed dishonesty in state companies and called the ruling party "the party of swindlers and thieves". "Navalny, who has for several years been lecturing the country about someone being a swindler and a thief, has himself been caught out in illegal acts," a senior ruling party official, Andrei Isayev, said in a comment on the party's website. On Tuesday, Navalny faced a scrum of television cameras with his usual confident demeanour, but spoke briefly and seemed shocked by the harsher charges which he called "mega-strange". He admitted that he could no longer rule out being arrested in the coming days or weeks. "It is possible," he said. "If it is possible for them to say that I stole those 16 million (rubles), then anything is possible."