Enrique Tarrio, Chairman of the Proud Boys, and Stewart Rhodes, founder of the Oath Keepers, attend a meeting in a garage in Washington, US, on January 5, 2021 (Reuters)

The FBI is probing a meeting between far-right leaders in a garage in downtown Washington a day before the January 6 Capitol riot aimed at undermining the results of the 2020 Presidential elections.

FBI witnesses said the meeting was between the then-leader of the far-right Proud Boys, now-arrested Oath Keepers militia leader, and other far-right figures.

The accounts mean that the heads of America's most notorious far-right Trump-supporting groups met each other just a day before the insurrection; however, three attendees told Reuters they did not discuss matters related to January 6.

Among the attendees was also the head of the pro-Trump "Latinos for Trump", Bianca Garcia, witnesses said, and another attendee said they discussed information related to criminal defense attorneys.

A House committee is conducting an investigation into the January 6 insurrection, which saw pro-Trump rioters seeking to block Congress from certifying President Joe Biden's election victory.

Proud Boys Chairman Enrique Tarrio had claimed that his garage meeting with his far-right counterparts was unplanned and insignificant, denying any Proud Boys planning ahead of January 6 though he fled DC after the meeting.

There were no reports about the FBI's probe nor the circumstances of the gathering, though many people affiliated with the leaders denied there being contact between them altogether.

Michael Simmons, who was present during the riots with Rohdes, said the latter never mentioned meeting with Tarrio, and upon hearing about the meeting, he said Rhodes had been critical of Tarrio and his group.

Federal prosecutors charged several Proud Boys and Oath Keepers leaders with playing key roles in the insurrection, though only Rhodes was indicted in the case.

To back their case, prosecutors cited the social media messages of one Oath Keeper leader indicted in the January 6 case. "This week I organized an alliance between Oath Keepers, Florida 3%ers, and Proud Boys," he wrote in a Facebook message ahead of the violence.

As of now, the Justice Department has not disclosed clear evidence that the far-right groups plotted an alliance on the day of the insurrection.