The co-founder of Telegram, Pavel Durov, is reportedly under investigation in Russia over allegations linked to terrorist activities, according to state newspaper Rossiyskaya Gazeta.
DPA reports authorities claim the messaging app has been used in a number of criminal cases, including references to the deadly attack at Crocus City Hall near Moscow, where more than 140 people were killed almost two years ago.
Durov responded on Telegram, accusing authorities of inventing reasons to restrict access to the platform and suppress privacy and free speech. He left Russia several years ago.
The development marks another step in a long-running dispute between Russian officials and the service.
Kremlin spokesperson Dmitry Peskov has repeatedly accused Telegram of failing to cooperate with authorities, saying the government has been forced to act.
Phone calls on Telegram have already been blocked in the country, and the service has recently been slowed down, according to reports.
Other messaging platforms, including WhatsApp and Signal, are also blocked in Russia.
