Ex-Trump adviser Roger Stone had regularly taunted Mueller before his arrest

Roger Stone, a longtime adviser to US President Donald Trump, was arrested Friday under an indictment issued by the special counsel examining possible collusion with 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 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 election.

It was the first indictment in months by the special prosecutor probing Russian efforts to tip the 2016 US election toward Trump and whether he and his people 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. His lawyer did not immediately respond to questions 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 over a dispute.

The two men, however, remained in close contact, the indictment underlying that Stone "maintained regular contact with and publicly supported the Trump Campaign through the 2016 election."

- Ready to testify? -

Stone had previously said he was ready to face possible charges from Mueller's team, and publicly taunted 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."