Deputy Attorney General Rod Rosenstein speaks during a news conference at the Department of Justice, Friday, July 13, 2018, in Washington. (AP Photo/Evan Vucci)

WASHINGTON – A dozen Russian intelligence officers have been charged with conspiring to hack Democrats during the 2016 presidential campaign, according to a new indictment in the probe led by special counsel Robert Mueller.

The 12 were members of Russian military intelligence, known as the GRU, and are accused of engaging in a sustained effort to hack the computer networks of Democratic organizations and the Hillary Clinton campaign.

Deputy Attorney General Rod Rosenstein detailed the new charges at a mid-day press conference. Mueller, as has been his practice, did not attend the announcement. Court records show a grand jury Mueller has been using returned an indictment Friday morning.

The announcement comes days before President Trump is due to meet with Russian President Vladimir Putin in Finland. Rosenstein said he briefed Trump earlier this week on the charges.

The 11-count indictment spells out in granular detail a carefully planned and executed attack on the information security of Democrats, implanting hundreds of malware files on Democrats’ computer systems, stealing information and then laundering the pilfered material through fake personas and others to try to influence voters’ opinions.

Rosenstein said the suspects worked to “hack into computers, steal documents, and release those documents with the intent to interfere with the election.”

The hackers also created false online personas, known as DC Leaks and Guccifer 2.0, to try to disguise the Russian origins of their work, Rosenstein said.

He said the hackers did interact with some Americans in the course of their efforts, but noted those people had not been charged with a crime.

“There’s no allegation in this indictment that any American citizen committed a crime. There’s no allegation that the conspiracy changed the vote count or affected any election result,” Rosenstein said. “The goal of the conspirators was to have an impact on the election. What impact they may have had… is a matter of speculation, that’s not our responsibility.”

Mueller and a team of prosecutors have been working since May 2017 to determine if any Trump associates conspired with Russia to interfere in the election. With the new indictment, his office has filed charges against 32 people on crimes ranging from hacking to money laundering to lying to the FBI. Twenty-six of those charged are Russians who are unlikely to ever be put on trial in the United States.

Trump’s former campaign manager, Paul Manafort, is in jail in Alexandria, Va., awaiting trial later this month on financial fraud charges stemming from activities that pre-dated the Trump campaign.

Mueller’s probe has come under sustained attack from Trump and his supporters in Congress, who call it a witch hunt and a politically-motivated attempt to hurt the president.

On Thursday, GOP lawmakers skewered FBI agent Peter Strzok at a congressional hearing over his work as the former lead agent in the Russia probe and an earlier investigation of Clinton’s use of a private email server when she was secretary of state. Over the course of a ten-hour hearing, Strzok fought back defending the FBI while also expressing regret for his personal statements expressing disdain for then-candidate Donald Trump.

The Washington Post’s Spenser S. Hsu contributed to this report.