Russia has warned Google, Twitter and Facebook to comply with laws requiring internet companies to transmit data on Russian bloggers who have more than 3,000 readers a day, Reuters has reported.

Russia’s communications, media and IT regulator Roskomnadzor has sent official notice to the three social media companies, reminding them to close down sites or pages that the watchdog deems to be calling for “unsanctioned protests and unrest”.

Russia passed a law last year which, according to critics, is nothing less than media censorship. The legislation allows Russian prosecutors to block sites without a court order. Other Russian legislation requires bloggers with large readerships to register with a government agency and have their identities verified.

In January the three companies resisted pressure to remove posts by opposition activist Alexei Navalny calling for a mass protest against President Vladimir Putin in Moscow. Thousands of people rallied at the unsanctioned demonstration, which passed off peacefully, despite dozens of arrests including Navalny who was seized by police for breaching a curfew order.

Google has said that it responded to about 5% of 134 requests for information from the Russian government during the second half of last year, and then only provided “some information.”

Twitter said it rejected 108 requests, and Facebook declined to respond to the only two requests it received last year.

If the companies did not pay more attention to Russian government requests for data “we will need to apply sanctions”, Reuters quoted Roskomnadzor spokesman Vadim Ampelonsky as commenting.

He didn’t specify what these sanctions might be but said that  because of the encryption technology used by the three social media giants, Russia had no way of blocking specific websites and so could only bring down particular content it deemed in violation of law by blocking access to their whole services.