Russia stepped up state oversight of internet activity on Wednesday by blocking the website of privacy service Tor, with the communications regulator accusing it of enabling access to illegal content.
The regulator, Roskomnadzor, said the website http://www.torproject.org had been prohibited on the basis of a court decision.
"The grounds for this were the placement of information on this website that enable the operation of tools that provide access to unlawful content," Roskomnadzor said in a statement.
"Today, access to the resource has been restricted."
Tor did not immediately respond to a Reuters request for comment.
Reuters verified that the Tor website was inaccessible. There was limited access to the Tor browser and other elements of the Tor infrastructure.
The Tor anonymity network is used to hide computer IP addresses in order to conceal the identity of an internet user.
Russia has sought to block at least 14 VPNs this year, but some services are still operational.
Foreign tech companies have been under increasing pressure over the content shared on their platforms, along with demands they set up offices on Russian soil, but Russia has also targeted virtual private networks (VPN), in a campaign critics say stifles internet freedom.