Russian authorities have blocked access to dozens of websites linked to jailed opposition leader Alexei Navalny.
Navalny's allies said on Monday that the Kremlin critic's official site had been restricted, as well as several others run by his close allies.
The website of Navalny's top strategist, Leonid Volkov, and longtime ally Lyubov Sobol were among 49 links that had been blocked.
Navalny’s Foundation for Fighting Corruption and the network of about 40 regional offices were outlawed as extremist groups last month.
Russia’s state communications watchdog, Roskomnadzor, confirmed access to all of the websites had been restricted after a request by the Russian prosecutor general’s office.
"The mentioned Internet resources are used for propaganda and the continuation of banned extremist activities of the FBK and Navalny's regional offices," the agency said in a statement to AFP.
The move comes amid mounting government pressure on opposition supporters, independent journalists, and human rights activists in Russia ahead of the country’s parliamentary election.
"They just completely decided to wipe us from the Russian Internet," said Navalny's associate Maria Pevchikh on Twitter.
Ivan Zhdanov, another close ally, said in an Instagram post that the politician’s team was "not surprised" that their websites had been blocked and that they had been "ready" for this.
Zhdanov urged supporters to follow Navalny’s team and its members on social media "where it’s harder to block us".
Navalny was arrested in January upon returning from Germany, where he spent five months recovering from a nerve agent poisoning that he blames on the Kremlin — an accusation that Russian officials reject.
In February, Navalny was ordered to serve 2 and 1/2 years in prison for violating the terms of a suspended sentence from a 2014 embezzlement conviction that he has dismissed as politically motivated.
His arrest and jailing sparked a wave of mass protests, followed by a number of arrests by the Kremlin and the criminal prosecutions of Navalny’s closest associates.
The court labeling of the politician’s Foundation for Fighting Corruption as an extremist group not only barred it from operating but also prevents people associated with the organisation from seeking public office.
The September election in Russia is widely seen as an important part of President Vladimir Putin’s efforts to cement his rule before a 2024 presidential election.
Navalny’s team has noted that the website of Smart Voting - a project to support any candidate most likely to defeat the Kremlin’s dominant United Russia party - remained available.
But strategist Volkov has suggested that authorities might block the strategy site "closer to the election".