Washington (Agencies): A federal grand jury on Friday indicted at least 12 Russian military intelligence officers on charges of hacking the computer networks of 2016 Democratic presidential candidate Hillary Clinton and the Democratic Party, the Justice Department said.

The indictment, secured by Special Counsel Robert Mueller in his investigation of Russian involvement in the 2016 election , was issued three days before US President Donald Trump meets Russian President Vladimir Putin for a summit in Helsinki.

It was the most detailed US accusation yet that Russia meddled in the election with the eventual aim of trying to boost Republican Trump’s campaign. Russia denies interfering.

“The indictment charges 12 Russian military officers by name with conspiring to interfere with the 2016 presidential election ,” Deputy Attorney General Rod Rosenstein told a news conference.

Rosenstein said there is no allegation that US citizens were involved in the alleged crimes described in the indictment. He said he briefed Trump earlier this week on the indictment.

Officers of Russia’s military intelligence agency, the GRU, “in their official capacities engaged in a sustained effort to hack into the computer networks of the Democratic Congressional Campaign Committee, the Democratic National Committee and the presidential campaign of Hillary Clinton,” a Justice Department news release said.

It said the officers then “released that information on the internet under the names DCLeaks and Guccifer 2.0.”

Mueller is investigating whether Trump’s campaign colluded with Russia and whether the president has unlawfully sought to obstruct the Russia investigation.

Mueller has secured indictments against several former Trump campaign aides, including former campaign chairman Paul Manafort, and former White House national security advisor Michael Flynn.

In February, Mueller charged 13 Russians and three Russian companies in an elaborate conspiracy to interfere in the election . That indictment said the Russians adopted false online personas to push divisive messages, travelled to the United States to collect intelligence and staged political rallies while posing as Americans.

But Friday’s indictment was the first by Mueller that directly charges Russia’s government with meddling.

US intelligence agencies have concluded that Russia, in an effort ordered by Putin, used propaganda and hacking to meddle in the election in an effort to harm Clinton and eventually help Trump.

A few hours before the indictments were announced, Trump described the Mueller investigation as a “rigged witch hunt” that is hurting the US relationship with Russia. Trump is currently on a visit to Britain.