MOSCOW (AP) — Russia's communications watchdog has begun enforcing a nationwide ban for the popular messaging app Telegram.

The Federal Communications Agency said Monday that Russian providers have been instructed to begin blocking Telegram after a court last week sided with authorities that had demanded that the app be blocked in Russia until it hands over the keys to its data encryption.

Telegram, which was developed by Russian entrepreneur Pavel Durov, argues that Russia's FSB intelligence service is violating consumer rights, while authorities say the app has been used by violent extremists.

Telegram was briefly unavailable to users early Monday afternoon but was back online later in the day. Durov said last week the latest version would have "built-in" features that would be able to circumvent the ban.