U.S. Special Counsel Robert Mueller disclosed for the first time Friday that his office has evidence of communications between Roger Stone, a longtime adviser to President Donald Trump, and WikiLeaks related to the release of hacked Democratic Party emails.

In a court filing on Friday, Mueller's office said it had gathered that evidence in a separate probe into Russian intelligence officers who were charged by Mueller of hacking the emails during the 2016 U.S. presidential campaign and staging their release.

In an email criticizing media coverage of Mueller's filing on Friday, Stone said the evidence was "innocuous Twitter direct messages" that have already been disclosed to the House Intelligence Committee and "prove absolutely nothing."