Moscow has blocked access to four websites run by opponents and critics of President Vladimir Putin.
The blog of opponent Alexei Navalny, two news sites and one run by Garry Kasparov were blocked on the orders of Russia’s prosecutor general’s office.
In a statement, it said the blocks were imposed because of the sites’ role in helping stage recent illegal protests.
Critics said the blocks were just the latest in a series of moves by Russia’s government to stifle dissent.
The blocks come as Russia’s central bank reported that hackers had targeted its main website. The site, and that of the Kremlin, were briefly unavailable with authorities saying “technical reasons” were making them hard to reach.