Russia's communications watchdog Roskomnadzor said on Monday it would check next year if Twitter has complied with the law requiring all companies to store personal data of Russian citizens on Russian soil.
"We can certainly say that we will check them until the end of 2018 to make sure they delivered on their promises," Roskomnadzor head Alexander Zharov told website RT.
Zharov referred to a letter from Twitter management saying the company planned to localise the data of the Russian citizens by mid-2018.
Last year Russia blocked access to social networking website LinkedIn, owned by Microsoft, after a court found the firm guilty of violating Russia's data law.
Roskomnadzor also said on Monday it had been informed by Google that the search engine does not change its algorithm to re-rank individual websites.
Google was responding to a request from Roskomnadzor regarding Russian media outlets RT and Sputnik, Roskomnadzor said on its website.
Google did not immediately respond to a request for comment.
Alphabet Executive Chairman Eric Schmidt, speaking at an international forum this month, responded to a question about Sputnik articles appearing on Google by saying the company was working to give less prominence to "those kinds of websites" as opposed to delisting them.