The Kremlin website was taken offline amid the Russian invasion of Ukraine.
Visitors to the page – on Kremlin.ru – could not load the site as usual.
The same problems were seen on other official websites, including the State Duma.
It follows similar outages in Ukraine in recent days. Hours before Russia began its invasion, the official websites of Ukraine’s parliament, government and foreign ministry were taken offline in what the country called a cyberattack.
Ongoing tensions between Russia and Ukraine have led to a wave of cyberattacks and other internet security activity, including these outages and the discovery of software wiping computers in the country.
Cybersecurity firm ESET said it identified destructive software circulating on hundreds of computers in the country, in what Ukrainian officials said was an escalating wave of hacks targeting the country.
The company said on Twitter that the data-erasing program had been installed on hundreds of machines in the country, an attack it said had likely been underway for two months.
Vikram Thakur of cybersecurity firm Symantec, which is also investigating the incident, told Reuters the infections had spread outside Ukraine.
“We are seeing activity across Ukraine and Latvia,” Thakur said. A Symantec spokesperson then added Lithuania.
It is unclear who is responsible for the wiper, although suspicion immediately fell on Russia, which has been repeatedly accused of launching data jamming hacks against Ukraine and other countries. Russia has denied the allegations.
Victims in Ukraine included a government agency and a financial institution, according to three people who have studied the malware since it was released.
The new cyberattack required existing access to operate, meaning those computer networks were already compromised, said Juan-Andres Guerrero-Saade, cybersecurity researcher at digital security firm SentinelOne.
Additional Reuters reports