Russia's media regulator has filed a lawsuit to block the encrypted messaging app Telegram in the country.
The watchdog Roskomnadzor is seeking to limit access to the app, a rival to WhatsApp, after the firm failed to give Russian FSB security service access to encrypted messages before a 4 April deadline.
It follows reports that Iran has also moved to block Telegram, which is used widely in Russia as well as the Middle East.
Roskomnadzor said its lawsuit, which aims to "restrict access" to Telegram in Russia, was connected to statements by the FSB that the app was not complying with its legal requirements as an "organiser of information distribution".
Last month, Pavel Durov, the founder and chief executive of Telegram, tweeted that threats to block the firm unless it gives up user data "won't bear fruit".
"Telegram will stand for freedom and privacy," said Durov, who is now based in Dubai.
Threats to block Telegram unless it gives up private data of its users won't bear fruit. Telegram will stand for freedom and privacy.
— Pavel Durov (@durov) March 20, 2018
The app's user base last month reached 200m, and last week the company revealed it had raised a total of $1.7bn (£1.2bn) thorough the world's biggest initial coin offering.