Russia’s Investigative Committee has launched a criminal case against Aleksei Navalny, accusing the Kremlin critic of stealing hundreds of millions of rubles donated to his anti-corruption organization.

The criminal case now raises questions as to whether Navalny, who is recuperating in Germany following his poisoning in August with a military-grade nerve agent, will return to Russia, where he could face a lengthy prison term if convicted.

Navalny dismissed the latest charges as the government’s revenge against him for surviving the poisoning and then exposing those who were behind it. The activist has called the poisoning an assassination attempt by the state’s security services.

“I immediately said: they will try to jail me for not dying and then looking for my killers. For proving that [Russian President Vladimir] Putin is personally behind everything. He is a thief, ready to kill those who refuse to keep quiet about his theft,” Navalny said in a tweet on December 29 shortly after the launch of the case.

Navalny has become a thorn in the Kremlin’s side over the years with his detailed investigations into corruption at the highest levels of government and has been jailed for short periods of time on several occasions.

His investigative videos — which often take him abroad to film the rich lifestyle of Russian officials — receive millions of views each time they are uploaded online and have helped sour the public on the government and the ruling party, United Russia.

The launch of a criminal case against Navalny comes amid an intensifying clampdown in recent years on the Kremlin opposition as the Russian economy struggles to grow and public frustration mounts over declining living standards.

Russia holds key parliamentary elections next year after what is likely to be the country’s worst economic performance in more than a decade. Navalny is seeking to weaken United Russia’s hold by urging his supports to vote for other candidates.

The Investigative Committee said in a post on December 29 that a series of nonprofit organizations run by Navalny, including the Anti-Corruption Foundation, raised a total of 588 million rubles ($7.94 million) from citizens.

Investigators claim he spent 356 million rubles ($4.81 million) acquiring personal items and vacationing abroad. They did not say what those items were, whether they were used to carry out his work, nor whether the alleged vacations coincided with the destinations he filmed.

Navalny later tweeted a link to his foundation’s donation page, telling his supporters that “the best way to laugh” at the new criminal case “invented” by the authorities was to finance his work.