Russia has blocked three major opposition news websites as well as the popular blog of Kremlin critic Alexei Navalny in a media crackdown that comes amid President Vladimir Putin's standoff with the West over Ukraine.
The government's media watchdog said late Thursday it was enforcing an order by prosecutors to add three popular opposition news websites to its banned list, along with Navalny's Live Journal blog.
The pulling of the sites openly critical of the Kremlin came as state media is waging a full-on propaganda war in support of intervention in the Ukrainian crisis and the Kremlin's incursion into Crimea after a popular uprising in Kiev last month.
The Internet has become practically the only outlet for opposition political views in Russia.
"There is an absolutely direct link with the events in Ukraine," said Alexander Podrabinek, a former dissident and a columnist for two of the newly banned websites, EJ.ru and Grani.ru.
"The authorities realised long ago these resources destroy their sunny picture of the world. Now is a good moment to swat them," Podrabinek told AFP.
The ban comes days after the chief editor of one of Russia's oldest and most popular news websites, Lenta.ru, was summarily dismissed on Wednesday over its Ukraine coverage.
Russian Internet providers were on Friday blocking access to the blacklisted websites, though they were still accessible through Internet providers outside Russia. Tips on how to get around the ban were circulating on social media.
The Roskomnadzor media watchdog said the sites were banned for "making calls for unlawful activity and participation in mass events held with breaches of public order," it said, apparently referring to opposition rallies.
"We will try to find out what we are being accused of and if we can restore the site's operations," said EJ.ru, which runs liberal opinion pieces.
A law that came into force in February allows the blocking of Internet sites on the order of prosecutors without a court decision.
'Final purge of media'
Roskomnadzor also announced that Navalny's blog was blocked because the anti-corruption campaigner was placed under house arrest last month and is banned from using the Internet.
His blog, which is fiercely opinionated and critical of Putin, is one of the most read on the Russian-language Internet.
Navalny, a charismatic opposition leader who came second in last year's race for Moscow mayor, has been confined to his Moscow apartment and banned from communicating with anyone except lawyers and family.
His blog was updated several times after his house arrest began, and one of the most recent posts on Wednesday criticised Russia's intervention in Crimea.
Earlier this week the state watchdog issued a warning to the Lenta.ru news website for "extremism" after it published interviews with leaders of Pravy Sektor, or Right Sector, an ultra-nationalist group that played a key role in the Kiev protests.
The sacking of veteran editor Galina Timchenko triggered an exodus of journalists.
"This is part of a general trend to close down everything outside the political mainstream of patriotic fervour, any expression of doubt about the authorities' actions," said media analyst Anna Kachkayeva.
"This is the path towards a final purge of media," she told AFP.
Other opposition media have come under threat of closure, including independent television channel TV Rain, which was dropped by cable providers last month after a row ostensibly about one of its talk shows insulting war veterans.
Prominent Russian blogger Anton Nossik said the authorities appeared to be getting ready to impose a full-blown blockade on independent media and social networks.
"It's necessary to prepare for the blockade of Live Journal, Facebook, Twitter, Dropbox and all Google resources," he said in an online post.