Russia will stop people accessing Facebook and Instagram in the country, making it a terrorist offence to do so.
Russia is in the process of declaring Meta, the owner of the sites, an "extremist organisation".
The move from the Kremlin comes a day after Reuters reported Meta had eased its guidelines to allow calls for Vladimir Putin and Belarus leader Alexander Lukashenko to be killed.
"A criminal case has been initiated ... in connection with illegal calls for murder and violence against citizens of the Russian Federation by employees of the American company Meta, which owns the social networks Facebook and Instagram," Russia's Investigative Committee said.
Using either site or app will be prosecuted under the same laws that is used on Isis terrorists.
"We don't want to believe the Reuters report - it is just too difficult to believe," Kremlin spokesman Dmitry Peskov told reporters on Friday."We hope it is not true because if it is true then it will mean that there will have to be the most decisive measures to end the activities of this company," Peskov added.
Instagram is the most popular media site in Russia and is seen as a vital tool for small businesses, so to lose it would be a huge blow to the general public.
Despite closing down Facebook and Instagram, Russia will allow WhatsApp to operate.