It's only for a limited group, but it's an certainly interesting move. According to Reuters, an Iranian official in the judiciary said that Telegram could only operate domestically with the permission of the government. It's quite possible that this could lead to a country-wide ban of the app.
This may also be a response to Russia's move against Telegram. That country has been waging its own sort of war against the service after founder Pavel Durov refused to hand over encryption keys to Russian officials. Last week, the country's courts granted the request for the app's banishment from the country, and Russia has started blocking all possible IP addresses that Telegram uses (which are owned by Amazon and Google).
Iran's government controlled media reported that Supreme Leader Ayatollah Ali Khamenei stopped using the service "in line with safeguarding national interests and removing the monopoly of the Telegram messaging app," according to Reuters. It remains to be seen whether Iran will take any further steps against the service in the future.