Russia's parliament has passed a law requiring Internet sites to store data of Russian citizens inside the country.
Under the law, from 2016 all Internet companies will have to move Russian data onto servers based in Russia.
The Kremlin says the move is aimed at protecting data.
Critics say it is an attack on social networks, namely Facebook, Twitter, and YouTube, all U.S.-based companies.
The State Duma action on July 4 comes after new rules requiring blogs attracting more than 3,000 daily visits to register with a communications watchdog and a regulation allowing websites to be shut without a court order.
Russian President Vladimir Putin has called the Internet a "CIA project," but denies he is restricting web freedoms, claiming his main aim was to protect children from indecent content.
Introducing the legislation earlier in the week, Russian lawmaker Vadim Dengin said "most Russians don't want their data to leave Russia for the United States, where it can be hacked and given to criminals."
"Our entire lives are stored over there," Dengin said.
Speaking to Reuters, Internet expert and blogger Anton Nossik claimed the Kremlin wanted to create a legal pretext to shut down inconvenient voices.
"The ultimate goal is to shut mouths, enforce censorship in the country and shape a situation where Internet business would not be able to exist and function properly."
Earlier this year, the Kremlin adopted a law giving authorities power to block websites deemed extremist or a threat to public order without a court ruling.
Among the websites blockers were those of Kremlin critics Aleksei Navalny and Gary Kasparov because they "contained calls for illegal activity."
Last month, a senior Twitter executive met the head of Russia's communications watchdog, Roskomnadzor, after it was asked to block a dozen unspecified accounts.
A Twitter spokesman later said the company had not agreed to block any accounts.
The State also broadened legislation on July 4 against incitement to separatism.
The law forbidding public calls judged to threaten Russia's territorial integrity had applied only to the news media.
But according to AFP, the law will now also cover ordinary bloggers, after the Russian parliament passed amendments banning all public incitement to separatism.
Analysts say the amended law could be aimed at those who disagree with Putin's internationally unrecognized annexation of Ukraine's Crimea region back in March.
"I believe this law is aimed at those who doubt that Crimea is ours," said Alexander Verkhovsky, director of the Sova Center, an NGO based in Moscow.
Based on reporting by AFP and Reuters