A dozen Russians have been charged with hacking Democratic Party emails during the 2016 US presidential election.
Rod Rosenstein, deputy US attorney general, announced the indictment against the intelligence officers as part of Special Counsel Robert Mueller's investigation into alleged collusion between Donald Trump's presidential campaign and Russia to help him secure a victory.
The 12 Russian officers are accused of hacking into the computer networks of the Democratic National Committee (DNC) as well as Hillary Clinton's presidential campaign.
Mr Rosenstein said the accused agents had stolen information on 500,000 American voters after hacking a state US election board.
The indictment also revealed that a candidate for US Congress asked for information and documents on their campaign opponent during the 2016 election.
"Between in or around June 2016 and October 2016, the conspirators used Guccifer 2.0 to release documents through WordPress that they had stolen from the DCCC [Democratic Congressional Campaign Committee] and DNC," it read. "The conspirators, posing as Guccifer 2.0, also shared stolen documents with certain individuals.
"On or about August 15, 2016, the conspirators, posing as Guccifer 2.0, received a request for stolen documents from a candidate for the US Congress.
"The Conspirators responded using the Guccifer 2.0 persona and sent the candidate stolen documents related to the candidate's opponent."
The investigation has already seen 20 people and three companies charged in relation to the allegations.
They include four former aides to President Trump's campaign and the White House, and 13 Russians who allegedly participated in a hidden social media campaign to sway public opinion during the election.
"The internet allows foreign adversaries to attack Americans in new and unexpected ways," said Mr Rosenstein, who added that he had briefed Mr Trump on the indictment.
"Free and fair elections are hard-fought and contentious and there will always be adversaries who work to exacerbate domestic differences and try to confuse, divide and conquer us."
However, he also said there was no allegation that any hacking had changed the vote count or that any Americans were knowingly in communication with the Russian agents.
A Kremlin aide has since aired concerns about the charges and the confiscation of Russian diplomatic property in the US.
Speaking ahead of Mr Trump meeting with Vladimir Putin on Monday, the aide said Russia was ready to look at the facts "if there are any".
Prominent Democrat Nancy Pelosi has called for the US president to demand a "comprehensive" agreement with Mr Putin that Russia will "cease their ongoing attacks on our democracy".
"Failure to stand up to Putin would constitute a profound betrayal of the constitution and our democracy," she added as other Democrats, including Senator Chuck Schumer, called for talks with Mr Putin to be cancelled.
Director of National Intelligence Dan Coats said Russia had been "the most aggressive" foreign actor targeting the US, adding that the "warning signs" were there.
Speaking earlier on Friday during his visit to the UK, Mr Trump said he would "absolutely" ask Mr Putin about the allegations of Russian election meddling.
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However, when asked about Mr Mueller's investigation, he branded it a "rigged witch hunt" and insisted he had been "tougher on Russia than anybody".
Russia has repeatedly denied being behind the nerve agent attack and rejected claims it interfered in the 2016 election.