Russia's media watchdog has blocked six providers of virtual proxy networks (VPNs), which people can use to circumvent government restrictions on the Internet.
The move, announced on September 3, comes as Russian authorities tighten control of the Internet, blocking access to dozens of websites ahead of parliamentary elections this month.
The Russian watchdog, Roskomnadzor, justified the new restrictions by saying that allowing access to blocked content "created conditions for illegal activities, including those related to the distribution of drugs, child pornography, extremism, and suicidal tendencies."
The targeted VPN providers, including the widely used Nord VPN and Express VPN, are among Russia's most popular, but several other companies offer similar services.
The Russian government in recent years has ramped up control over the Internet under the guise of fighting extremism and protecting minors.
Critics have denounced official oversight of the web as censorship aimed at silencing dissent.
The authorities have also stepped up repression of opposition lawmakers and activists ahead of Russia's nationwide legislative elections, which are scheduled for September 17-19, with nearly all vocal Kremlin critics barred from running.