Russian internet watchdog Roskomnadzor blocked 49 websites linked to Kremlin critic Alexei Navalny on Monday,
The Moscow Times reported
His personal website Navaly.com has also been blocked.
There he published his investigations into alleged government corruption, which have sparked protests across Russia in recent years.
Navalny.com has been inaccessible since Monday afternoon.
On the site is the message that access is restricted based on the Russian information law.
In a statement, the internet watchdog said it had blocked the websites linked to Navalny for "propaganda and prohibited extremist activities".
Leonid Volkov, an ally of the exiled Navalny, claims nearly fifty sites linked to the imprisoned opposition figure were blocked simultaneously.
The website of lawyer Lyubov Sobol, who represents Navalny's foundation FBK, and that of Navalny's regional political network have also disappeared.
FBK suspects that the authorities will soon also block Navalny's website Smart Voting.
There, supporters can get information about election candidates who are critical of the Kremlin so that they can vote strategically.
In June, FBK was banned by a Moscow judge.
The ruling sparked international criticism.
"By banning the anti-corruption organization and political network of Kremlin critic Navalny, Russia is going further than ever before," the European Union said.
However, FBK says it will ignore the ban.
Navalny, who is in a penal colony herself, responded to the ruling via an announcement on Instagram.
He acknowledged that his supporters now have to adjust their working methods.
"But we stick to our goals and ideas. This is our country and our only country."