Regulator Roskomnadzor said the website was banned based on a court ruling.
“The motives for this were the placement of information on this website which enables the operation of tools for accessing illegal content,” Roskomnadzor said in a statement.
“Today, access to the resource has been restricted.”
Tor, which was founded by American computer scientists, said that without access to its service, hundreds of thousands of people would no longer have a secure way to communicate both in Russia and around the world.
The Tor anonymity network is used to mask the IP addresses of computers in order to conceal the identity of an Internet user. Tor, which claims its mission is to advance human rights and freedoms, claims it has more than 300,000 users in Russia, or 14% of all daily users, just behind the United States.
Reuters has verified that the Tor website is inaccessible. Access to the Tor browser and other elements of the Tor infrastructure was limited.
GlobalCheck, a group that monitors website accessibility in Russia, has confirmed that the block has started.
In a blog post posted on Tuesday, Tor said some ISPs started blocking access since December 1 and urged its users to bypass the block by visiting its mirror site, which is still functioning.
âBlocking Tor would be next to impossible. It is a large community that will find the means to finance the organization of the bypass of the blockade in Russia, âsaid Mikhail Klimarev, head of the Internet Defense Society, a nonprofit group that seeks to fight censorship in online in Russia.
Anton Gorelkin, a member of the State Duma’s Committee on Information and Communications, this week described Tor as a cover for illegal activity and “absolute evil”.
Tor responded, âBy making a comment that rejects the need for such technology, or trying to present it that way, governments are obscuring reality: Tor and technology like it are lifelines. “
(Reporting by Alexander Marrow, Gleb Stolyarov and Anton Zverev; editing by Elaine Hardcastle, David Evans and John Stonestreet)