The watchdog said in September it would block Facebook starting next year unless the social network complied with a law requiring websites that store the personal data of Russian citizens to do so on Russian servers.

"In the near future Roskomnadzor will plan a series of supervisory activities aimed at analyzing the activities of the administration of Facebook in terms of the processing of Russian users' personal information, the terms of services for users, and the content of existing legislation," it said in a statement on Wednesday carried by the Interfax news agency.

Russian authorities say the law, introduced in 2014, is aimed at protecting Russians' personal data.

Critics, however, see its use as an attack on social media in a country that has tightened its control over the Internet in recent years.

Last year Roskomnadzor blocked access to LinkedIn to comply with a court ruling that found the networking service guilty of violating the same data storage law.

LinkedIn Corp. has yet to come to an agreement with Russian authorities to restore public access to the service.

(Reporting by Christian Lowe; Writing by Gabrielle Tétrault-Farber; Editing by Richard Balmforth)