Moscow has blocked access to the blog of popular anti-Putin leader Alexei Navalny, who is in house arrest, along with other independent news sites.
The state communications monitoring agency, Roskomnadzor, included LiveJournal and other opposition sites in a register of banned pages at the request of Russia's general prosecutor's office.
The independent sites grani.ru, kasparov.ru and ej.ru allegedly contain "incitement to illegal activity and participation in mass activities conducted in violation of the established order", reads a statement on Roskomnadzor's website.
Navalny's blog was blocked because it allegedly violated the terms of the campaigner's two-month house arrest, which included a ban on the use of any communication devices and the internet.
The opposition leader is serving a five-year suspended sentence for his part in the embezzlement of 16 million roubles (£300,000) worth of timber from a state-owned company, while working as an adviser for the governor of the region four years ago.
House arrest was imposed because he repeatedly travelled outside Moscow in breach of sentencing conditions.
Navalny, who is also defendant in an embezzlement and money laundering investigation known as the Yves Rocher Case, insisted that the charges were in retaliation for his role in protests in 2011 and 2012 opposing Putin's rule.
Russian blogger Oleg Kashin called the website ban a provocation.