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(CNN) —  

Former Trump campaign chairman Paul Manafort has denied ever meeting Julian Assange, following a report he had met with the WikiLeaks founder at least three times in previous years.

On Tuesday, The Guardian reported that Manafort had secretly met several times with Assange inside the Ecuadorian Embassy in London, including around the time he was made a top figure in the Trump campaign. The Guardian, citing sources, said Manafort had met with Assange in 2013, 2015 and in the spring of 2016.

Manafort responded to The Guardian’s report by calling it “totally false and deliberately libelous.”

“I have never met Julian Assange or anyone connected to him,” Manafort said in a statement. “I have never been contacted by anyone connected to Wikileaks, either directly or indirectly. I have never reached out to Assange or Wikileaks on any matter. We are considering all legal options against the Guardian who proceeded with this story even after being notified by my representatives that it was false.”

The newspaper said it is unclear “why Manafort wanted to see Assange and what was discussed.”

Both WikiLeaks and Manafort feature prominently in special counsel Robert Mueller’s investigation into Russian interference in the 2016 US election and whether the Trump campaign colluded with Moscow. In a court filing on Monday, Mueller accused Manafort of lying to investigators after agreeing to cooperate with the special counsel’s office.

Citing a “well-placed source,” The Guardian reported that Manafort had met with Assange around March 2016, just months before WikiLeaks released Democratic emails believed to be stolen by Russian intelligence officers.

Manfort’s lawyers declined to answer the Guardian’s questions about the visits.

The newspaper also reported that an internal document written by Ecuador’s intelligence agency and seen by The Guardian contains Manafort’s name on a list of “well-known” guests at the embassy in 2013. The list, according to the newspaper, also mentions “Russians.”

Jennifer Robinson, Assange’s UK-based counsel, told CNN that”no such meetings took place.”

“We have had no contact with the Mueller investigation,” she added.

WikiLeaks denied the report shortly after it was published, tweeting:

“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.”

Barry J. Pollack, an attorney for Assange who was in federal court in Virginia for an unrelated issue Tuesday, said he didn’t “know whether that’s accurate or not” when asked about the meetings detailed in the report.

For more than a year now, Manafort has been at the heart of several unresolved threads of the Mueller investigation. He had been in the room for the Trump Tower meeting with Russians who touted they had incriminating information about Hillary Clinton; and he had allegedly offered private briefings on the campaign to a Russian oligarch to whom he was indebted, according to The Washington Post.

Manafort pleaded guilty to conspiracy and witness tampering on September 14, almost a year after he was first charged and following his conviction by a jury in a separate but related case on eight tax and banking crimes.

In another development, CNN contributor Carl Bernstein reported Tuesday that Mueller’s team has been investigating a meeting between Manafort and Ecuadorian President Lenin Moreno in Quito in 2017 and has specifically asked if WikiLeaks or Assange was discussed in the meeting, according to a source with personal knowledge of the matter.

In November 2017, The Associated Press reported that Moreno publicly acknowledged meeting with Manafort and a group of Chinese businessmen who wanted to privatize the country’s electric corporation. Moreno said the proposal was rejected.

This is a breaking story that has been updated.

CNN’s Devan Cole, Kara Scannell and Laura Jarrett contributed to this report.