In a sign of new limits on Facebook’s ability to serve as a platform for political opposition movements, Russian users appear to have been blocked from accessing a page calling for a protest in support of a prominent dissident.

In 2011, Facebook was hailed by opposition movements during the Arab Spring and in Russia as a powerful new tool to spread information beyond the control of repressive governments. That may no longer be the case, at least not in Russia. Russian Internet regulators said Saturday that they had sent Facebook a “demand” that it block access to a page calling for a demonstration in support of Alexei Navalny, the most prominent critic of Russian President Vladimir Putin.

The page was set up on Friday after prosecutors recommended that Navalny be sent to prison for 10 years in a criminal case that critics have said is purely politically motivated. Within hours, the page drew thousands of people who said they were planning to attend, and as of Saturday evening, the number stood at more than 12,300. But it was no longer visible to users inside Russia. “This content is currently unavailable,” the Web site told users who tried to access it from inside the country.

A Facebook spokeswoman said the company was investigating the matter. Several similar pages, apparently set up Saturday after the first one was blocked, were still visible early Sunday in Moscow.

Russia’s Internet regulator said it had asked Facebook to block the page because it called for an “unauthorized mass event.” Under a Russian law that went into effect in February, the regulator is empowered to block pages that call for protests that would “infringe the public order.”

Facebook users in Russia appear to have been blocked from accessing a page calling for a protest in support of a prominent dissident. (Dado Ruvic)

The organizers of the protest had said on Facebook that they did not plan to obtain a permit for the action.

“At the moment, the demand” to block the page “is being fulfilled” by Facebook, Vadim Ampelonsky, a spokesman for the Russian Internet regulator, told the Interfax news service.

Facebook, Twitter and other social networks typically work to comply with the laws of the countries in which they have a physical presence. Facebook is popular among Russia’s large and active Internet-using population. The company said that it blocked 29 pieces of content within Russia in the first half of 2014 at the Russian government’s request.

Twitter has also blocked accounts within Russia after being ordered to do so by the regulators.

On Friday, prosecutors requested that Navalny receive a 10-year prison sentence and that his brother Oleg be sentenced to eight years for their alleged involvement in stealing nearly $500,000 from two companies, one of which is an affiliate of the French cosmetics firm Yves Rocher. Navalny has denied the allegations. Yves Rocher employees say no crime was committed.

Navalny, an anti-corruption blogger, became the most prominent leader of the opposition protests that started in December 2011. They were the largest rejection of Putin’s authority during his 15 years ruling the country. Navalny has been under house arrest since February. The sentencing is expected to take place Jan. 15.