Russia has begun enforcing a nationwide ban on the popular messaging service Telegram. A Russian government agency said on Monday that it had sent a notice to telecommunications providers to block Telegram. The order came from the Federal Service for Supervision of Communications, Information Technology and Mass Media. Last Friday, a Russian court ruled against the messaging service. The court said Telegram should be blocked until it obeys a government order to provide users’ encrypted messages to the Federal Security Service. Russian officials have said they need to read the messages to investigate the use of Telegram by violent extremist groups. Telegram has repeatedly refused to surrender access to messages, arguing this would violate its users’ privacy. The service is the creation of Russian businessman Pavel Durov, who criticized the ban Monday in a statement on social media.