Russia has not ruled out targeting the messaging service Viber for failing to grant security services access to users’ private communications, a minister said.

Russia’s communications regulator Roskomnadzor has disrupted unrelated online services in its attempts to enforce an April court order banning Telegram for refusing to turn over encryption keys to the Federal Security Service (FSB). Tech firm representatives, including Telegram founder and CEO Pavel Durov, have maintained that providing encryption keys or gaining access to information beyond the device is impossible.

Viber, one of Russia’s most popular messaging apps, restored service this week after accessibility problems that resulted from the regulator’s ongoing Telegram ban.