The demonstration - between Pushkinskaya subway station and Sakharov Prospekt - was staged on Sunday against online censorship and demanded the "exoneration of Russians prosecuted for posting content online."

Demonstrators shouted: "No to censorship, no to dictatorship!" and "Down with the police state!" Some adapted a popular slogan from opposition rallies against President Vladimir Putin's rule, shouting "Russia without Putin and censorship!"

The OVD Info website - which monitors detentions of political activists - said three people had been detained, one for giving out leaflets promoting opposition leader Alexei Navalny.

Protesters highlighted the case of video blogger Ruslan Sokolovsky - who filmed himself hunting Pokemons in a church and has been placed on a list of "terrorists" and extremists and had his bank accounts blocked.

They also demanded the release of mathematician Dmitry Bogatov, who was arrested on charges of organizing riots and alleged calling for terrorism through the internet.

They also want the resignation of the chief of the Roskomnadzor, the state censor.

Size isn't everything

According to Russian news outlet Meduza, city authorities allowed up to 10,000 people to gather for the march. A journalist for the French news agency AFP estimated the turnout at 1,000 to 1,500. According to the police, about 800 people took part.

The protest was organized by the Parnas opposition party, headed by former Prime Minister Mikhail Kasyanov. 

The Russian website The Real Times reported that the protests were also organized by the Democratic Choice Party, the Party of December 5, the Pirate Party of Russia, the Libertarian Party and the "Roskomvoboda" movement.

Threats to free internet

The state has recently clamped down on several companies operating in the country, including LinkedIn and Telegram and is pushing for restrictions on the use of virtual private networks (VPNs).

On the eve of the protests, the State Duma passed a bill that prohibits the use of anonymizers and VPN services that allow access to internet resources blocked in the territory of Russia.

The bill was developed by Roskomnadzor on the initiative of the Security Council of Russia. Its authors argue that this will help limit access to extremist materials.

A last bastion of relative freedom

The internet is one of the country's few forums for political debate and Kremlin critic Navalny has won a youth following with live video blogs and YouTube videos.

Human Rights Watch (HRW) released a report last week condemning the Russian government's censorship of the internet, revealing in detail how  authorities have "intensified a crackdown on freedom of expression" in recent years.

Pavel Rassudov - the former head of the Pirate Party campaign group – told AFP that "restrictions on the internet began in 2011," as the opposition to Putin held mass rallies in Moscow.

"The authorities realized the internet was a tool for mobilization, that it brings people out onto the streets," Rassudov said.

Russia - he said - has imposed restrictions on internet use, blacklisting web pages for extremist content and prosecuted a growing number of individuals for posting online

Since January 1 internet companies have been required to store all users' personal data at centers in Russia and provide it to the authorities on demand.

According to Google's annual report, Russia has become the world leader in the number of requests for the removal of information from Google's search results and other company services, in particular from YouTube.