Citing a “well-placed source,” The Guardian states Manafort visited Assange in 2013, 2015, and around March 2016, roughly the time he joined Trump’s campaign. What may have been discussed at these alleged meetings is unknown.

WikiLeaks denied via Twitter that any such meeting took place. In a series of tweets beginning shortly after The Guardian‘s article published Tuesday, WikiLeaks barraged the newspaper for publishing what it claims is false information and called for the editor’s resignation.

Remember this day when the Guardian permitted a serial fabricator to totally destroy the paper's reputation. @WikiLeaks is willing to bet the Guardian a million dollars and its editor's head that Manafort never met Assange. https://t.co/R2Qn6rLQjn

— WikiLeaks (@wikileaks) November 27, 2018

If the meeting between Manafort and Assange did take place, it could be of interest to special counsel Robert Mueller.

Four months after their alleged meeting, in July 2016, WikiLeaks released nearly 20,000 emails from Democratic National Committee officials that were hacked by Russian operatives. The emails showed DNC officials worked against the presidential campaign of Sen. Bernie Sanders. The event damaged the DNC’s reputation and led to the resignation of chairwoman Debbie Wasserman Schultz.

Manafort denies any involvement in this hacking, according to The Guardian.

The former campaign manager has already been found guilty of several counts of fraud by a federal jury earlier this year. He reached a plea deal with federal prosecutors a few months ago to avoid a second trial, but Mueller recently said Manafort violated this deal by lying to the FBI.