On a post on his VK page, Durov said:
This morning the Russian authorities blocked Telegram, therefore the service could be unstable with some telecom operators. The consequences of blocking are:
1. The quality of life for 15 million Russians will worsen as Telegram without VPN could be inaccessible at times.
2. The terrorist threat in Russia will remain at the same level as extremists will continue using all sorts of encrypted communication channels — in other messengers or via VPN.
3. The national security of Russia will in fact decrease, as some of the personal data of Russians will be moved from the neutral service (to the Russians) to US-controlled WhatsApp / Facebook.
We consider the decision to block [Telegram] anticonstitutional and will continue defending the right to privacy of correspondence for Russians.