US President Donald Trump's longtime ally Roger Stone was arrested on Friday on charges of obstruction, witness tampering and making false statements related to the release of stolen Democratic Party emails during the 2016 presidential campaign.

Stone, an adviser to Trump in his unorthodox bid for the White House, was arrested in the predawn darkness on Friday and scheduled to appear at the federal courthouse in Fort Lauderdale, Florida, at 11am local time (16:00 GMT).

The indictment ends months of speculation that Stone would be charged as part of Special Counsel Robert Mueller's probe into Russia's alleged interference in the 2016 campaign to help Trump defeat Hillary Clinton.

On Twitter, Trump called the probe "the greatest with chunt in the history of our country".

Stone was charged with seven criminal counts accusing him of lying to Congress about his public statements and communications with others suggesting he may have had advance knowledge of plans by Wikileaks to release hacked emails.

His lawyer, Grant Smith, told Reuters news agency that Stone would "vigorously" contest the charges.

"There was no collusion," Smith said. "He forgot to tell something to Congress and what it was was immaterial."

He appeared briefly in federal court in Fort Lauderdale, Florida, wearing blue jeans and a blue polo. A judge released him on a $250,000 bond and ordered him to limit his travel to South Florida, New York City and Washington, DC.

WikiLeaks, which is referred to as "Organisation 1" in the indictment, did not respond to a request for comment.

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The charging documents included new details about the activities of Trump aides, including an incident in which a senior campaign official "was directed to contact Stone about any additional releases and what other damaging information Organisation 1 had regarding the Clinton Campaign".

Barbara McQuade, a former US Attorney for the Eastern District of Michigan, said "the indictment was not unexpected, but it is still significant because it alleges coordination between the Trump Campaign and WikiLeaks."

Stone is one of the closest Trump associates to be charged by Mueller.

'Obstruction, false statements'

Stone was charged with one count of obstruction of an official proceeding, five counts of making false statements and one count of witness tampering, according to the indictment. The charges relate to Stone's testimony before congressional committees probing Russian meddling in the 2016 presidential election.

CNN, in video of the arrest, showed a heavily armed FBI team taking Stone away from his home just before 6am local time (11:00 GMT) on Friday and Stone surrendering without any issue.

Michael Caputo, a longtime Stone associate and former Trump campaign adviser, said he expected Stone to fight the charges.

"This has been rumoured to be coming down for several months, so Roger and his legal team are ready to fight these charges in court," Caputo told Reuters.

"They can't prove collusion or conspiracy because it doesn't exist, so they're going after him personally. He will be vindicated."

A self-described "agent provocateur" of the American right and Republican veteran of Washington and New York City politics, Stone has a tattoo of the face of late president Richard Nixon on his back. His political career began with the Nixon presidential campaign in 1972.

The indictment described in detail numerous emails and text messages "during the 2016 campaign in which he discussed Organisation 1, its head, and its possession of hacked emails".

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Stone still possessed many of those communications when he gave false testimony about them, prosecutors said in the indictment.

He also tried to persuade a witness to provide false testimony and withhold information from the congressional investigations, the indictment said.

Senator Mark Warner, the top Democrat on the Senate Intelligence Committee, had no immediate comment, according to an aide. Representatives for the heads of the two congressional committees that interviewed Stone could not be immediately reached.

US prosecutors pointed to two other individuals, including an unnamed political commentator with an online publication who regularly spoke with Trump throughout the campaign, a description that matches Jerome Corsi.

They also described a radio host who Stone had known for more than 10 years, which matches the profile of Randy Credico. Corsi declined to comment and Credico did not immediately respond to request for comment.