The indictment also does not allege that any vote tallies were altered by hacking.
Still, Deputy Attorney General Rod Rosenstein said the internet "allows foreign adversaries to attack Americans in new and unexpected ways. 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."
Before Friday, 20 people and three companies had been charged in the Mueller investigation. The 20 are four former Trump campaign and White House aides, three of whom have pleaded guilty to different crimes and agreed to cooperate, and 13 Russians accused of participating in a hidden but powerful social media campaign to sway U.S. public opinion in the 2016 election.
If the involvement of the GRU officers in the hacking effort is proved, it would shatter the Kremlin denials of the Russian state's involvement in the U.S. elections.
The GRU, which answers to the Russian military's General Staff, is part of the state machine and its involvement would indicate that the orders to interfere in the U.S. election came from the very top.
Hours before the Justice Department announcement, Trump complained anew that the special counsel's investigation is complicating his efforts to forge a better working relationship with Russia. Trump and Putin are scheduled to hold talks Monday in Finland, a meeting largely sought by Trump.
After the indictments were announced, top Senate Democrat Chuck Schumer called on Trump to cancel his meeting with Putin until Russia takes steps to prove it won't interfere in future elections. He said the indictments are "further proof of what everyone but the president seems to understand: President Putin is an adversary who interfered in our elections to help President Trump win."
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."
Referring to Mueller's probe, he said: "We do have a - a political problem where - you know in the United States we have this stupidity going on. Pure stupidity. But it makes it very hard to do something with Russia. Anything you do, it's always going to be, 'Oh, Russia, he loves Russia.'"
"I love the United States," Trump continued. "But I love getting along with Russia and China and other countries."
Associated Press writers Richard Lardner, Desmond Butler and Mary Clare Jalonick in Washington and Raphael Satter in Paris contributed to this report