WASHINGTON — Twelve Russian military intelligence officers hacked into the Clinton presidential campaign and Democratic Party, releasing tens of thousands of stolen and politically damaging communications, in a sweeping conspiracy by the Kremlin to meddle in the 2016 U.S. election, according to a grand jury indictment announced days before President Donald Trump’s summit with Russian President Vladimir Putin.

The indictment stands as special counsel Robert Mueller’s first allegation implicating the Russian government directly in criminal behavior meant to sway the presidential election.

U.S. intelligence agencies have said the meddling was aimed at helping the Trump campaign and harming the election bid of his Democratic opponent, Hillary Clinton. The effort also included bogus Facebook ads and social media postings that prosecutors say were aimed at influencing public opinion and sowing discord on hot-button social issues.

The indictment lays out a broad, coordinated effort starting in March 2016 to break into key Democratic email accounts, such as those belonging to the Democratic National Committee, the Clinton campaign and the Democratic Congressional Campaign Committee. Among those targeted was John Podesta, the Clinton campaign chairman.

The Kremlin denied anew that it tried to sway the election. “The Russian state has never interfered and has no intention of interfering in the U.S. elections,” Putin’s foreign affairs adviser, Yuri Ushakov, said Friday.

But the indictment identifies the defendants as officers with Russia’s Main Intelligence Directorate of the General Staff, also known as GRU. It accuses them of covertly monitoring the computers of dozens of Democratic officials and volunteers, implanting malicious computer code known as malware and using phishing emails to gain control of the accounts of people associated with the Clinton campaign.

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By June 2016, the defendants began planning the release of tens of thousands of stolen emails and documents, the indictment alleges. The messages were released through fictitious personas like DCLeaks and Guccifer 2.0.

The charges come as Mueller continues to investigate potential coordination between Russia and the Trump campaign to influence the presidential election. The indictment does not allege that Trump campaign associates were involved in the hacking efforts or that any American was knowingly in contact with Russian intelligence officers.

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.”

A White House statement offered no condemnation of the alleged Russian conspiracy. Instead it focused on the fact that no Trump campaign officials or Americans were implicated in the new indictment. Trump’s lawyer, Rudy Giuliani, said on Twitter that it was time to end the Mueller investigation since “no Americans are involved.”

But with Mueller still investigating, it’s not known whether further indictments are taking shape or will.

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.

One attempt at interference noted in the indictment came hours after Trump, in a July 27, 2016, speech, suggested Russians look for emails that Clinton said she had deleted from her tenure as secretary of state.

“Russia, if you’re listening,” Trump said, “I hope you’re able to find the 30,000 emails that are missing.”

That evening, the indictment says, the Russians attempted to break into email accounts used by Clinton’s personal office, along with 76 Clinton campaign email addresses.

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 complained about “stupidity” when asked about Mueller’s probe earlier Friday, at a news conference in Britain with Prime Minister Theresa May.

“We do have a — a political problem where — you know in the United States we have this stupidity going on,” he said. “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.”