Russian authorities have stepped up efforts to curb weekend demonstrations against the detention of Kremlin critic Alexei Navalny.
The opposition leader was detained on Sunday on his return to Russia on charges of parole violation. It was the first time he had set foot in the country since his poisoning in August with a Novichok nerve agent. Navalny has accused the Kremlin of ordering his murder, which Moscow has denied.
Navalny's supporters have called for nationwide demonstrations to take place in 65 Russian cities on Saturday, accusing the Russian government of corruption.
But Russia's interior ministry had described the planned protests as "illegal" and stated it is ready to "protect public order".
Meanwhile, the prosecutor general’s office has called for websites and social media platforms to be restricted if they are used to call people to participate.
More than 4,000 people have also signed up on Facebook for a demonstration in Moscow. Meanwhile, many short videos posted by Russian users on the popular video-sharing platform, TikTok, have also shown support for Navalny.
Young users on the app have filmed themselves packing items, seemingly in preparation for upcoming rallies, while others were seen replacing portrait's of President Putin on their classroom walls with images of Navalny.
In total, videos shared using the hashtag #23января (#23January) have more than 134 million views.
In a post on his Instagram page, Navalny quoted his lawyer as saying that "schoolchildren" have caused "mayhem" on TikTok.
"I don't know what that means, but it sounds cool," the Kremlin critic added.
But tech giants like Facebook and Twitter have been ordered by Russia to "block all publications with calls to demonstrate on the 23rd".
"Calls for participation in illegal mass events have been identified ... and prosecutorial response measures are taken," the prosecutor's office said in a statement.
"Requirements have been submitted to the Federal Service for Communications, Information Technology and Mass Communications to restrict access to illegal information."
Russia's communications watchdog, Roskomnadzor, also ordered TikTok and Russia’s largest social network, VKontakte, to prevent young audiences from being encouraged to demonstrate.
The authority also threatened platforms with a fine of up to four million roubles (€44,600) if they failed to remove "prohibited information".
"Internet sites will be brought to administrative responsibility in connection with the dissemination of information prohibited by law and aimed at attracting minors to participate in unauthorised mass public events," the watchdog said.
"Participation in such events is in violation of the established procedure, including in a pandemic, and carries risks of harm to life and health."
In a later statement on Friday, Roskomnadzor said that social networks had begun "removing calls for children to participate in illegal mass events."
The watchdog said that TikTok had removed 38% of prohibited content, while VKontakte had taken action on 50% of "illegal information", and Instagram 17%.
Meanwhile, video-sharing platform YouTube had stopped distributing 50% of the videos calling for young people to join the weekend's rallies, the authority said.
On Thursday, to further stem the calls for protest, Russian police also arrested Lyubov Sobol, a rising figure in Russia's opposition and a noted ally of Navalny, as well as several other of his associates.
Meanwhile, opposition supporters and independent journalists have been warned against demonstrating across the country by police officers, while universities and colleges have also urged students not to take part.