The group also allegedly conspired to hack into computers of state election boards, secretaries of State and US companies that supplied software and other technology related to election administrations.
At the same press conference, Trump appeared to directly call upon Russian intelligence services to hack the former secretary of state's email account and to publish any information they stole as a part of their cyber-espionage operations within the 2016 presidential elections.
President Trump is scheduled to meet with Russian President Vladimir Putin in Helsinki, Finland, on Monday.
Rosenstein asked Americans to focus not only who was hurt by or benefited politically from the Russian attacks but to unite against foreign influence in the American democratic process.
All three worked out plea deals and have pledged to cooperate with the investigation.
Eleven of the 12 Russians are charged with money laundering, aggravated identity theft, and conspiracy to commit computer crimes.
The indictment connects the officers directly to the Russian government, saying they acted in their "official capacity".
All migrant kids under 5 to be back with parents by Thursday
The Trump administration is missing its court-imposed deadline to reunite 102 young immigrant children with their parents. The government has until July 26 to reunite almost 2,800 other children, ages five through 17, now in its custody.
If the Russian Federation probe is a "witch hunt", then Robert Mueller is a goddamn Ghostbuster.
■ They also hacked into the computer networks of the Democratic Congressional Campaign Committee and the Democratic National Committee, monitoring the computers of dozens of committee employees, implanting hundreds of files containing malware, and stealing e-mails and other documents.
"There is no allegation in the indictment that any American was a knowing participant in the alleged unlawful activity or knew they were communicating with Russian intelligence officers", Rosenstein said Friday while announcing the charges.
Trump said at a news conference Friday near London with British Prime Minister Theresa May that he wasn't going into the meeting with Putin with "high expectations".
The longtime GOP strategist acknowledged to CNN that messages included in the latest indictments match ones that he previously released relating to the hacker Guccifer 2.0, but he denied that he is the person referred to in the indictment "because I wasn't in regular contact with members of the Trump campaign".
One of the Russian units worked to steal information, and another was created to disseminate the information, Rosenstein said. Presidential lawyer Rudy Giuliani on Friday tweeted that the indictments are good news - Russians have been nailed, no Americans are involved, and it's time for Mueller to wrap up his "pursuit of the President". Rosenstein told reporters the timing of the release had nothing to do with the upcoming summit.
The defendants are named in the indictment as Viktor Netyksho, Boris Antonov, Dmitry Badin, Ivan Yermakov, Aleksey Lukashev, Sergey Morgachev, Nikolay Kozachek, Pavel Yershov, Artem Malyshev, Aleksandr Osadchuk and Aleksey Potemkin.