Russia accused the United States on Tuesday of leading a massive campaign of "cyber aggression" behind hundreds of thousands of malicious attacks a day while Russia has troops in Ukraine.
The foreign ministry said media, critical infrastructure and life support systems had been targeted, with the unprecedented scale pointing at US and NATO-trained special forces as well as hackers acting on behalf of Kyiv's western sponsors.
"The sources of attacks will be identified and the attackers will inevitably be held accountable for their actions in accordance with the law," the Russian statement said.
NBC News reported last month that US President Joe Biden had been presented with options that included disrupting Russia's internet, power and railroad switches. But the White House said that was "wildly off base."
Biden has said Russia may be planning a cyber attack against the United States, but the Kremlin has denied that.
The foreign ministry said it believed Ukraine's government, which in February announced the formation of an "IT army", was involved and had launched an "offensive cyber force".
The cybersecurity arm of Russia's telecoms firm Rostelecom and Russia's digital ministry have both reported cyber attacks.