On Tuesday, Roskomnadzor blocked millions of IP addresses that were used to get around the Telegram ban.
"If you have a government agency being so brutal attacking Telegram, taking down millions of IP addresses, after that you can do what you want", said Andrei Soldatov, one of the authors of "The Red Web", a history of the Russian internet.
Retailers, online games and another message service - Viber - are also said to have been affected.
The block reportedly comes as a result of the Russian group Roskomnadzor's attempts to block Internet users from using Telegram, an encrypted messaging service. Roskomnadzor threatened with the trial if Telegram would not pass the encryption keys to the FSB.
Russia's Roskomnadzor watchdog began blocking Telegram, a messaging service popular in Russian Federation, on Monday after it refused to comply with a court order to grant state security services access to its users' encrypted messages.
He later added that fewer than 7% of Telegram's users are in Russian Federation but that it was "personally" important for him to help them.More news: Cubs and Cardinals postponed Wednesday due to inclement weather
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Russian Federation has threatened to block Facebook as the authorities attempt to extend their control of the Internet and shut down the encrypted messaging service Telegram.
Roskomnadzor might block Facebook, if the social network does not comply with the requirements of the Russian law.
Most of Russia's state bodies have migrated their Telegram channels to TamTam, a messenger owned by Kremlin-linked oligarch Alisher Usmanov's Mail.ru Group, in compliance with last week's court order. The watchdog has faced trouble in blocking Telegram, since it is using Amazon and Google's cloud servers.
Many users of the Odnoklassniki social network say they have been unable to publish new posts or open old ones, according to the Mediazona news website.