Russia's media regulator on Friday blocked six providers of virtual proxy networks (VPN), protected networks that people can use to access websites that are blocked.
Virtual private networks promote "illegal activities" such as drug trafficking, extremism and child pornography, the Russian authority Roskomnadzor said in a statement.
Thousands of internet sites are blocked in Russia, including many associated with people critical of the government, as well as independent media or outlets that produce reporting that questions the regime.
The authorities attribute the restrictions by saying that, without them, Russian laws would be broken. But critics call the moves censorship, as freedom of expression is increasingly restricted.
All of the affected VPN providers are among Russia's most popular. They are all based abroad, including ExpressVPN and NordVPN, information technology experts say. However, several other companies offer similar services.
Russia moved to ban the use of VPN networks to circumvent blocked websites in 2017.
Then, three months ago, the use of two providers was restricted. After that, prices for VPNs rose significantly, according to research by Kommersant newspaper, a trend that observers attributed to higher demand.
Russia is due to conduct parliamentary elections in just more than two weeks. In past months, the authorities have stepped up repression of opposition lawmakers and activists.