Bitcoin has become a significant funding source for one of Russia's leading political dissidents.

Alexei Navalny, a politician believed by many to be President Vladimir Putin's main opponent, has attracted more than 591 BTC in donations over the last three years, worth about $3 million at current prices, public blockchain data shows.

The donations became a flashpoint this week when a pro-Putin television network questioned their timing.

Navalny's investigative center, the Anti-Corruption Foundation (FBK), regularly publishes exposés of government officials, including prime minister Dimitri Medvedev and attorney general Yuri Chaika.

On Monday, an anonymous Telegram channel, "FBK Staffer's Confession,"  noted that the Navalny organization's wallet received several large donations a few days before FBK published one such investigation, insinuating it was a paid hit piece. The claim was covered in Russian media, including the pro-Putin Tsargrad TV.

When contacted by Russian news publication Znak, FBK's chief of staff Leonid Volkov denied any connection between the transactions and its investigations, saying the anonymous blogger "dragged the non-existent facts together in by the head and shoulders."

Volkov added:

The Navalny wallet (3QzYvaRFY6bakFBW4YBRrzmwzTnfZcaA6E, listed on the donations page of his website) received its first bitcoin in December 2016 and since then has seen more than 2,000 transactions, including withdrawals, according to blockchain data.

Most transactions were worth from a fraction of a bitcoin to several bitcoins. From time to time, larger transactions occurred, bringing in up to 20 BTC at once.

Yet Navalny's political movement, which also accepts donations via bank transfers and PayPal, is not the only dissenting voice in Russia to take cryptocurrency.

Investigative outlets including Zona.Media and The Insider, as well as internet freedom movement Roskomsvoboda, accept donations in bitcoin or ether. However, their wallets have accumulated only small amounts of crypto, no more than 2 BTC each.

Alexei Navalny image via Shutterstock