Roger Stone, a longtime adviser to Donald Trump, was arrested Friday under an indictment issued by the US special prosecutor examining possible collusion between the president's campaign and Russia.
Stone was charged with seven counts, including obstruction of an official proceeding, making false statements and witness tampering, according to Special Counsel Robert Mueller's office.
The indictment concerns Stone's communications with WikiLeaks founder Julian Assange, whose group leaked tens of thousands of stolen Democratic Party emails that embarrassed Trump's rival Hillary Clinton in an apparent bid to influence the 2016 presidential election.
But Stone was not accused in the document of conspiring with Assange or Russian officials.
The White House rejected the idea that the noose was getting tighter around Trump, who has denied any collusion with Russia.
"This has nothing to do with the president and certainly nothing to do with the White House," spokeswoman Sarah Sanders told CNN.
It was the first indictment in months by the special prosecutor probing Russian efforts to influence the election and whether Trump and his aides tried to obstruct justice.
FBI agents arrested Stone at his home in Fort Lauderdale, Florida before dawn, and he is due in federal court there later in the day.
CNN broadcast footage of the pre-dawn operation. One agent pounded on the door and shouted: "FBI. Open the door."
Stone's lawyer did not immediately respond to a request for comment.
Stone, who launched his career as a campaign aide to Richard Nixon and has a tattoo on his back of the first US president to resign from office, has spent decades advising various US political campaigns.
He was one of the first members of Trump's team when the billionaire real estate magnate formally announced he was seeking office, but he left months later.
The two men, however, remained in close contact, with the indictment saying that Stone "maintained regular contact with and publicly supported the Trump Campaign through the 2016 election."
The indictment said Trump campaign officials contacted Stone about future releases of stolen emails by WikiLeaks, referred to as "Organization 1," after a first dump on July 22, 2016, indicating the campaign was aware of the moves before they occurred.
It was unclear which Trump campaign official was initially directed to contact Stone about the WikiLeaks releases.
Stone's contacts over the cache of documents were also revealed to be far more extensive than previously known.
"On or about October 4, 2016, the supporter involved with the Trump campaign asked Stone via text message if he had 'hear(d) anymore from London,'" the indictment said.
"Stone replied, 'Yes -- want to talk on a secure line -- got WhatsApp?' Stone subsequently told the supporter that more material would be released and that it would be damaging to the Clinton campaign."
According to the indictment, Stone also tried to cover up his actions by lying about it to Congress and pushing another witness to refuse to speak to the House Intelligence Committee as well, in one case using an analogy from one of the "Godfather" movies.
"On multiple occasions, including on or about December 1, 2017, Stone told Person 2 that Person 2 should do a 'Frank Pentangeli' before HPSCI in order to avoid contradicting Stone's testimony," it said.
When testifying before the Senate in the film, the Pentangeli character declares "I don't know nothin' about that" when questioned about his possible links to the mafia.
Mueller's indictment quoted a radio interview between Stone and "Person 2" that shows the unnamed individual is comedian Randy Credico.
Stone had previously said he was ready to face possible charges from Mueller's team, and publicly criticised the special counsel, echoing Trump's claims of a "witch hunt."
"This was supposed to be about Russian collusion, and it appears to be an effort to silence or punish the president's supporters and his advocates," he told NBC's "Meet The Press" in May.
"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," Stone said. "I would chalk this up to an effort to silence me."
Stone has also previously insisted that he would never testify against Trump.
"There's no circumstance under which I would testify against the president, because I'd have to bear false witness against him," he told ABC's "This Week" in December. "I'd have to make things up, and I'm not going to do that."