The event is only the latest installment in a series of attacks against the Russian government's IT infrastructure after the country invaded Ukraine.
Russian government websites face unprecedented cyberattacks, TASS news agency cited the country's digital ministry.
Officials claim to be trying to filter foreign web traffic to minimize impact. The description of the preventive measures resembles a step that an agency might take in preventing a distributed denial-of-service (DDoS) attack.
Accessing several Russian government sites appears to be severely limited at the time of publication, with loading times of up to several minutes.
The ministry was working to adjust to the new conditions, it said, as cyber attacks ratchet up.
"If previously their power at peak moments reached 500 gigabytes, then now it is at 1 terabyte. That is two to three times more powerful than the most serious incidents of this kind that have been previously reported," the ministry said.
Several Russian government and media sites were raided by hacktivists from around the world after Moscow invaded Ukraine on the night of February 24.
Cyber activists targeted Russian state-controlled media outlets TASS, Kommersant, Izvestia, Fontanka, and RBC, pushing them offline.
Russian carrier Aeroflot and major lender Sberbank were also experiencing outages and access issues recently.
In light of the attack, the hacker community started rallying to help Ukrainians. With Anonymous being the most prominent one, numerous hacker groups and researchers partake in various campaigns to help Ukraine.
The German branch of the Anonymous collective also claims to have stolen 20 terabytes of data from the German arm of Rosneft, Russia's state energy company.
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