A federal grand jury has charged 12 Russian intelligence officers with hacking Democratic Party computer networks in 2016, the most detailed US accusation yet that Moscow meddled in the presidential election to help Republican Donald Trump.
The indictment, which alleges a wide-ranging conspiracy involving sophisticated hacking and staged releases of documents, raises the stakes for a summit next week between President Trump and Russian President Vladimir Putin.
Officers of Russia's military intelligence agency, the GRU, covertly monitored computers of Democratic candidate Hillary Clinton's campaign and Democratic campaign committees, and stole large amounts of data, the indictment said.
"In addition to releasing documents directly to the public, the defendants transferred stolen documents to another organisation, not named in the indictment, and discussed timing the release of the documents in an attempt to enhance the impact on the election," Deputy US Attorney General Rod Rosenstein said.
Friday's indictment was secured by Special Counsel Robert Mueller as part of his probe into Russian involvement in the election.
It was the first by Mueller that directly charges the Russian government with meddling in the election, which Trump unexpectedly won. The Kremlin denies it interfered.
Rosenstein said he briefed Trump earlier this week about the indictment. It contains no allegations that US citizens committed a crime.
A few hours before the indictments were announced, Trump called the Mueller investigation a "rigged witch hunt" that is hurting the US relationship with Russia.
The Russian foreign ministry said the indictment aimed to damage the atmosphere before the summit. It said there was no evidence that the 12 people charged were linked to military intelligence or hacking.
Trump said he would "absolutely, firmly ask" Putin about the meddling at their planned meeting in Helsinki on Monday. But several prominent Democratic lawmakers called on Trump to cancel the summit.
US intelligence agencies concluded in January 2017 that Russia, in an effort ordered by Putin, used propaganda and hacking to meddle in the election to harm Clinton and eventually help Trump.
But the 29-page document describes several incidents in which the alleged Russian hackers, using the internet personas DCLeaks and Guccifer 2.0, were in contact with Americans.
It says that Russian operatives provided direct assistance to a candidate for the US Congress, who in August 2016 requested and received from Guccifer 2.0 documents stolen from the DCCC about their opponent. The candidate and the person's party affiliation were not identified.
That same month, the indictment says, "the Conspirators, posing as Guccifer 2.0, sent a reporter stolen documents pertaining to the Black Lives Matter movement," which was a sensitive political issue for the Democratic Party.
The indictment says the Russian operatives wrote to an unnamed person "who was in regular contact with senior members" of the Trump campaign.
Longtime Trump ally Roger Stone told CNN that he thought he "probably" was the person referred to in the indictment.
"There is no evidence in this indictment that I or anyone involved with Donald Trump received anything from the Russians or anyone who hacked the material and passed it to WikiLeaks," Stone told CNN.