Political strategist Roger Stone, a long-time ally of President Trump, has been arrested in Florida, charged with seven counts in the Mueller probe.
Mr Stone will appear in court later in the city of Fort Lauderdale.
The charges are linked to an alleged Russian-led hack into the emails of Democratic Party officials.
The information contained in the emails was released by WikiLeaks during the 2016 US presidential election campaign.
CNN reports that FBI agents arrested Mr Stone in a pre-dawn raid on Friday. One pounded on the door and said, "FBI... Open the door," the US outlet says.
What links Stone to the email hack?
Hillary Clinton's 2016 campaign chairman John Podesta, who was targeted in the email hack, accused Mr Stone of knowing about it beforehand.
More than a month before the emails were made public, Mr Stone tweeted it would soon be Mr Podesta's "time in a barrel", which some critics say was a reference to his prior knowledge of the hack.
Mr Stone has denied having advanced knowledge of the hack and any knowing contact with Russian agents.
On Friday, Mr Podesta referenced the cryptic tweet in a post about Mr Stone's indictment, noting it was "Roger's time in the barrel".
According to investigators, Mr Stone said he had "communicated" with WikiLeaks founder Julian Assange before the emails' release and had described the contact as "perfectly legal".
The indictment accuses the lobbyist of lying to the House Intelligence Committee about what passed between him and WikiLeaks, and of falsely claiming not to have records of it.
Mr Stone is said to have spoken to senior Trump campaign officials - who are not identified - about "organization 1" [believed to be WikiLeaks] "and information it might have had that would be damaging to the Clinton Campaign".
Prosecutors say Mr Stone was also "contacted by senior Trump campaign officials to inquire about future releases" by WikiLeaks.
His campaign activities have long been under scrutiny by Special Counsel Robert Mueller, who is investigating allegations of collusion between Russia and the Trump campaign.
In 2016, US intelligence agencies concluded that Russia had tried to turn the election in Mr Trump's favour through a state-authorised relay of cyber attacks and fake news stories planted on social media.
The Mueller investigation has also focused on Mr Stone's communications with Twitter persona Guccifer 2.0, which US intelligence officials say is a front for Russian military intelligence.
Mr Trump has branded the Mueller inquiry a political "witch-hunt". The Kremlin has always denied meddling in the US election.
An attorney for Mr Stone told CNN his client's misstatements were "immaterial" and merely due to forgetfulness.
"Roger Stone is vindicated by the fact there was no Russian collusion," the unnamed attorney said, also noting Mr Stone had received nothing from Wikileaks ahead of the release.
On Friday White House Press Secretary Sarah Sanders said the indictment "has nothing to do with the president" and there was no evidence of collusion.
Mr Stone has repeatedly said in interviews that he expected to be indicted. In May he told NBC's Meet The Press: "It is not inconceivable now that Mr Mueller and his team may seek to conjure up some extraneous crime pertaining to my business, or maybe not even pertaining to the 2016 election.
"I would chalk this up to an effort to silence me."
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