Russian telecom watchdog Roskomnadzor said Tuesday it will punish Twitter and Facebook if they decline to move the databases of Russian users to Russia.
"The companies will either have to localize the databases within a certain period of time, which I suppose will be about nine months, or they will be punished," Roskomnadzor head Alexander Zharov said.
He said he expected Twitter and Facebook representatives to meet with Roskomnadzor officials in Moscow by the end of February to discuss the issue.
Russian legislation requires Internet service providers to store and process personal data of Russians on the territory of Russia.
Roskomnadzor has the right to impose fines on or even block Internet companies for their violations.
In December, it fined Google 500,000 rubles (around 7,625 U.S. dollars) for failing to remove search links to banned information.
Last year, Roskomnadzor attempted to block instant messaging app Telegram in Russia due to its refusal to provide user data, but failed for technical reasons.