(CNN) Special counsel Robert Mueller has indicted 13 Russian nationals and three Russian entities for allegedly meddling in the 2016 presidential election, charging them with conspiracy to defraud the United States, the Department of Justice announced Friday.

In addition, three defendants were charged with conspiracy to commit wire fraud and bank fraud, and five defendants with aggravated identity theft.

"The defendants allegedly conducted what they called information warfare against the United States, with the stated goal of spreading distrust towards the candidates and the political system in general," Deputy Attorney General Rod Rosenstein said.

Mueller had convened a grand jury as part of his investigation into Russian interference in the 2016 election as well as any possible connections between Russia and Trump campaign associates.

The sweeping indictment describes in detail an unprecedented campaign by Russia to influence the 2016 presidential election, affirming the longstanding conclusions of the US intelligence community. It is at odds with President Donald Trump's repeated questioning of those conclusions, which has continued throughout his first year in office. CNN reported this week that Trump is still not convinced that Russia meddled in the election.

Trump emphasized the lack of allegations of any impact on the presidential election.

"Russia started their anti-US campaign in 2014, long before I announced that I would run for President," he tweeted. "The results of the election were not impacted. The Trump campaign did nothing wrong - no collusion!"

In a statement, the White House said Trump was fully briefed on the indictment and "is glad to see the Special Counsel's investigation further indicates— that there was NO COLLUSION between the Trump campaign and Russia and that the outcome of the election was not changed or affected."

"(I)t is more important than ever before to come together as Americans," Trump said in the statement. "We cannot allow those seeking to sow confusion, discord, and rancor to be successful. It's time we stop the outlandish partisan attacks, wild and false allegations, and far-fetched theories, which only serve to further the agendas of bad actors, like Russia, and do nothing to protect the principles of our institutions. We must unite as Americans to protect the integrity of our democracy and our elections."

A White House official told CNN that Rosenstein and FBI Director Christopher Wray briefed the President on the indictment at the White House on Friday morning, but the White House later said Wray did not attend the briefing.

Indictment details

Beginning as early as 2014, the Russian organization Internet Research Agency began operations to interfere with the US political system, including the 2016 elections, according to the indictment.

The defendants allegedly posed as US persons, created false US personas and operated social media pages and groups designed to attract US audiences, the indictment reads. Two of the Russians also allegedly traveled to the United States in 2014 to gather intelligence for their operations.

The Internet Research Agency had a "strategic goal to sow discord in the US political system" including the election, according to the indictment.

Russians posted "derogatory information about a number of candidates," according to the indictment. They bought ads and communicated with "unwitting" people tied to the Trump campaign and others in order to coordinate political activities.

The indictment mentions a February 2016 memo to Internet Research Agency staff telling them to post political content on US social media sites and "use any opportunity to criticize Hillary and the rest (except Sanders and Trump — we support them)." The reference to Trump and Sen. Bernie Sanders, the Vermont independent who challenged Clinton for the Democratic nomination, shows that the Russian government decided early on to oppose Clinton.

Twelve of the 13 defendants charged worked for the Internet Research Agency.

Rosenstein said Friday that the indictment does not contain any allegations that any Americans knowingly participated in the activity.

"There is no allegation in this indictment that any American was a knowing participant in this illegal activity," he said. "There is no allegation in the indictment that the charge conduct altered the outcome of the 2016 election."

Rosenstein added that the special counsel's investigation is ongoing.

Despite Rosenstein's caveat, the indictment does detail communications between unnamed Trump campaign officials and the Russian defendants.

The three campaign officials, identified only as campaign officials 1, 2 and 3, were involved in the Trump campaign's Florida operation, the indictment says. On at least three occasions, as detailed in the indictment, American personas created by the defendants wrote to the campaign officials, in some instances about rallies they were organizing.

In one instance, a Russian persona wrote to one Florida campaign official identifying 13 "confirmed locations" where they would be holding rallies in the state and asked the campaign to provide "assistance in each location," according to the indictment.

The indictment does not say whether the unnamed campaign officials ever responded to the Russian personas.

Social media tactics

According to the indictment, the Russians created an email address, allforusa@yahoo.com, to purport to be a US person in order to send out press releases in June 2016 for a "March for Trump" rally to New York media outlets.

The defendants allegedly used a Facebook account belonging to a fictitious person named Matt Skiber, posing as an American to contact a real US citizen to act as a recruiter for the rally, even offering money to print posters and buy a megaphone.

The advertisements weren't limited to Trump. They also allegedly purchased ads on Facebook to promote "Support Hillary. Save American Muslims" rally to allege Clinton was supporting Islamic law. They also allegedly bought ads to promote a "Down with Hillary" rally.

The defendants focused on key purple states during the election. The Skiber account allegedly sent a private message to a real Facebook account, "Florida for Trump," to offer support. They also allegedly used a stolen identity of a real US citizen to email grassroots groups in Florida.

The defendants allegedly attempted to cover their tracks after social media companies, including Facebook, publicly disclosed in September 2017 that they had identified Russians purchasing political and social advertisements on its platform and after media reports noted the company was cooperating with the special counsel's investigation.

"We have a slight crisis here at work: the FBI busted our activity (not a joke). So, I got preoccupied with covering tracks together with colleagues," one of the defendants wrote, according to the indictment.

One of the named defendants, Yevgeny Prigozhin, is a Russian oligarch who has been dubbed Russian President Vladimir Putin's "chef" by the Russian press. According to the indictment, Prigozhin controlled Concord Catering, a group that funded the Internet Research Agency. By around September 2016, the indictment says, the Internet Research Agency's monthly budget for the project that included the US election interference operation exceeded 73 million Russian rubles, or over $1.25 million.

Prigozhin said he was "not at all upset" he was named in the indictment.

"Americans are very impressionable people, they see what they want to see," Prigozhin told the Russian state news agency RIA Novosti. "I have great respect for them. I'm not at all upset that I'm on this list. If they want to see the devil, let them see one."

The indictment also alleges that some of the defendants traveled to the United States to "gather intelligence." Over a three week trip in June 2014, two of the named defendants made stops in at least seven states, including Colorado, Michigan, Texas and New York, the indictment says.

The defendants took extensive precautions on travel to the United States, the indictment alleges. They "planned travel itineraries, purchased equipment (such as cameras, SIM cards, and drop phones), and discussed security measures (including 'evacuation scenarios')," it says.

Russian Foreign Ministry spokesperson Maria Zakharova described the indictment Friday as "absurd."

"(Thirteen) people intervened in the elections in the US?" she wrote on her Facebook page. "13 against billion-dollar budgets of special services? Against intelligence and counterintelligence, against the latest developments and technologies? ... Absurd? Yes."

"This is modern American political reality," she added in the post.

Facebook's vice president of global policy, Joel Kaplan, said in a statement that the company has "more to do to prevent against future attacks. We're making significant investments, including increasing the number of people working on security from 10,000 to 20,000 this year. We're also continuing to work closely with the FBI, the Department of Homeland Security and other companies on better ways to protect our country and the people on our platform."

"We're committed to staying ahead of this kind of deceptive and malevolent activity going forward," Kaplan added.

Congressional reaction

House Speaker Paul Ryan called the Russians' alleged actions "a conspiracy to subvert the process, and take aim at democracy itself."

"We have known that Russians meddled in the election, but these indictments detail the extent of the subterfuge," Ryan said in a statement. "These Russians engaged in a sinister and systematic attack on our political system. It was a conspiracy to subvert the process, and take aim at democracy itself. Today's announcement underscores why we need to follow the facts and work to protect the integrity of future elections."

House Minority Leader Nancy Pelosi said in a statement that the indictments "make absolutely clear" that Russians tried to influence the presidential election to support Trump's campaign and continue to try to interfere with our elections.

"We are on the eve of the 2018 midterm elections," the statement added. "There is no time to waste to defend the integrity of our elections and our democracy."

Former CIA Director John Brennan said he thought the actions alleged in the indictments would have influenced some US voters, going further than the stated position of the US intelligence community.

"DOJ statement and indictments reveal the extent and motivations of Russian interference in 2016 election," Brennan tweeted. "Claims of a 'hoax' in tatters. My take: Implausible that Russian actions did not influence the views and votes of at least some Americans."

The ranking Democrat on the Senate Intelligence Committee, which is also investigating Russian interference in the 2016 election, said in a statement that he is "glad" to see the committee's work "vindicated" by the indictments.

"With this indictment, the Special Counsel and his team have taken an important step to hold Russia accountable," Sen. Mark Warner of Virginia said Friday.

Senate Minority Leader Chuck Schumer said in a statement that given the indictments, Trump should "immediately" implement the Russia sanctions that Congress passed last summer to punish Moscow for its election meddling.

"The administration needs to be far more vigilant in protecting the 2018 elections, and alert the American public any time the Russians attempt to interfere," Schumer said.

Clinton, through her spokesman, Nick Merrill, declined to comment on the indictments, but Merrill said the indictments "confirm what we've long known. Time will tell us more, but Russia went to great lengths to undermine our democracy, and the President won't protect us. No matter your politics, it's un-American. We have an adversary that is laughing at us, who will act again."

Robby Mook, Clinton's former campaign manager, tweeted: "The intelligence community has repeatedly told us Russia meddled. Now criminal indictments from DOJ. We were attacked by a foreign adversary. Will our Congress and President stand strong and take action? Or let it happen again?"