The US Department of Justice has charged 12 Russian intelligence officers with hacking Democratic officials in the 2016 US elections.
Deputy Attorney General Rod Rosenstein said the dozen accused used spear phishing emails and malicious software.
He said the hackers also stole data on half a million voters from a state election board website.
The Kremlin said there was no evidence linking the 12 to military intelligence or hacking.
The claims were “an old duck” and a “heap of conspiracy schemes”, said Moscow’s foreign ministry in a statement.
Friday’s indictment was the first by US officials to directly charge Russia’s government with meddling in the US vote two years ago.
The 11-count indictment names the Russians defendants, alleging they began cyber-attacks in March 2016 on the email accounts of staff for Hillary Clinton’s presidential campaign.
Mr Rosenstein said the defendants corresponded with several Americans during the alleged conspiracy, but added there is no allegation that any US citizen committed a crime.
The deputy attorney general said the conspirators used fictitious online personas, including “DCLeaks” and “Guccifer 2.0”, to release thousands of stolen emails beginning in June 2016.
They also plotted to hack into the computers of state boards of elections, secretaries of state, and voter software, according to the indictment.
Mr Rosenstein said: “We know that the goal of the conspirators was to have an impact on the election.”
The deputy attorney general said all 12 defendants were in the Russian intelligence service, the GRU.