According to a report in RT.com late Monday, Roskomnadzor, the Russian censorship agency, said that Facebook and Twitter failed to comply with a law requiring all servers that store personal data to be located in the country.
"The tech giants instead handed 'formal answers' to the authorities' previous inquiries. The agency also pledged to take legal action against the internet companies," said the report.
Russian privacy laws require foreign online service providers to store users' personal data on servers located within the country.
Roskomnadzor sent letters to Facebook and Twitter on December 17, giving them 30 days to provide "a legally valid response".
After no responses, the agency said that "Roskomnadzor begins administrative proceedings against both companies", reported The Wall Street Journal.