Facebook and sites of independent media such as the BBC and German broadcaster Deutsche Welle will be inaccessible in part of Russia on Friday.
Both local journalists from the AFP news agency in Moscow and GlobalCheck, a group that monitors the internet connection, report the blockade.
Europe previously announced that it would cut off access to news sites of Russian state media RT and Sputnik. Britain already feared that the blockade could lead to a similar action by Russia, making European media in the country no longer accessible.
Whether all Russians are struggling with the problems is currently unclear.