Roger Stone, a former adviser to President Donald Trump, was indicted by special counsel Robert Mueller and arrested Friday on charges of obstruction, giving false statements and witness tampering.

Stone has been under the microscope of Mueller over his alleged connection to WikiLeaks and hacked Democratic emails released by the site during the 2016 presidential campaign. He has repeatedly denied any collusion with WikiLeaks. 

Stone, 66, was arrested in Fort Lauderdale, Florida, and is expected to make an initial appearance later Friday in a federal courthouse.

Stone was an official with the Trump campaign as of August 2015, although "maintained regular contact with and publicly supported" the campaign through the 2016 election, according to the grand jury indictment filed Thursday in the U.S. District Court for the District of Columbia.

Nearly a dozen Stone associates have been summoned by Mueller to appear before his Washington grand jury, sources told NBC News in November.