Russian Watchdog to Ask Twitter, Facebook for Personal Data Localization in Dec.

Earlier this year Roskomnadzor also warned Facebook that the company might be fined for failing to store users' data locally, adding that social media giant didn't act fast enough to delete illegal content.

"When the second half of the year comes to an end, I set a deadline for me on December 15, I will write a letter: tell me where this data is stored. They will answer something to me. I will do the same regarding Facebook," Roskomnadzor head Alexander Zharov told reporters.

The official addressed a letter Twitter had sent to Roskomnadzor which was stating that in the second half of 2018 the company would localize the data of Russian users on the territory of the country.

READ MORE: Twitter Suspends 4,000 Accounts Allegedly Linked to Russia — CEO

The storage of Russian users' personal data within the Russian borders became obligatory due to a law, adopted by the parliament in 2015.

These measures are connected to the amendments to the legislation on personal data protection in effect since September 1, 2015, requiring foreign companies operating in the country to store the data of the Russian users within the Russian borders. Roskomnadzor has the legal authority to ban the companies, which can't comply with the law.