The Russian state telecommunication regulator is blocking access to Telegram messenger app, following the refusal of the company to provide access to encrypted messages of users.

Telegram, which is run by a Russian founder, Pavel Durov, has more than 200 million users, and is a favorite messaging app due to privacy concerns.

According to Russian regulators, Telegram is classified as a platform for the dissemination of information, and is consequently required to provide the keys to its encryption service to Russia’s Federal Security Service. Supposedly this is to enable them monitor suspected terrorists.

Russian communications regulator Roskomnadzor had on March 20 given Telegram 15 days to comply with this request. Durov publicly denounced the order, saying Telegram will stand for freedom and privacy.

In a statement on Monday, Roskomnadzor said that he had notified telecommunication operators about blocking access to Telegram within Russia. He is carrying out a decision by a Russian court that ruled on Friday that the messaging company should be blocked for not abiding by Russian regulations. Several ISPs have already complied with this directive.