Russia's telecoms watchdog plans to probe Facebook before the end of the year after blocking access in the country to the popular messaging app Telegram, its head said on Wednesday.
"We will conduct a probe of the company before the end of 2018," the head of state regulator Roskomnadzor, Alexander Zharov, told pro-Kremlin newspaper Izvestia.
Russia's telecoms regulator has repeatedly warned Facebook it could be banned this year unless it complies with a law on the personal data of Russian nationals.
A 2014 law requiring foreign messaging services, search engines and social networking sites to store the personal data of Russian users inside the country has caused widespread concern as it is seen as putting the information at risk of being accessed by Russian intelligence services.
Zharov told Izvestia that Facebook still did not comply with the Russian legislation.
"They are already significantly late in their deadlines and in complying with other laws," Zharov said, referring to Facebook.
"The question of a ban will be raised" if Facebook does not fully comply with the law, he said, adding that he meets with representatives of the social media giant "around once every half a year."
Roskomnadzor began blocking the popular messaging app Telegram on Monday after a court banned the service for refusing to give the security services access to private conversations.
The ruling came after a long-running battle between the Russian authorities and Telegram, which has a reputation for securely encrypted communications, as Moscow pushes to increase surveillance of internet activities.
Telegram, a free application that lets people exchange messages, stickers, photos and videos, has attracted more than 200 million users since its launch by Russia's Pavel Durov and his brother Nikolai in 2013.
On Tuesday, Roskomnadzor blocked millions of IP addresses that were used to get around the Telegram ban.
Facebook and Telegram are widely used by the opposition to President Vladimir Putin to coordinate protests and make political statements.
The Kremlin's press service also used Telegram to communicate with journalists but earlier this week switched to ICQ, a 1990s chat service now controlled by Kremlin-friendly billionaire Alisher Usmanov.