Special counsel Robert Mueller's team has asked the FBI to look into claims that women were offered money to fabricate sexual assault allegations against Mueller, who leads the probe into Russia's attempts to influence the U.S. election in 2016.

"When we learned last week of allegations that women were offered money to make false claims about the Special Counsel, we immediately referred the matter to the FBI for investigation," Peter Carr, a spokesperson for Mueller, said in a statement Tuesday.

The Federal Bureau of Investigation declined to comment.

Multiple U.S. news outlets are reporting that the alleged plot came to light when journalists were emailed on Oct. 17 by a woman who says she was asked to make false claims against Mueller. That email was reportedly among those referred to the FBI.

The woman says she was contacted because she had worked with Mueller in 1974 as a paralegal. According to The New York Times, she said the man offered her more than $50,000 US to "make accusations of sexual misconduct and workplace harassment against Robert Mueller."

She also told the Times that the man told her he was working for Jack Burkman.

Burkman is a Washington lawyer and Republican operative. He told Reuters he has spoken to five women who claim they were sexually assaulted by Mueller, and denied paying them for the information.

He said he would have a news conference close to Washington on Thursday with one of the women who claimed she was sexually assaulted by Mueller in 2010, and that the other four women still needed to be vetted.

Burkman, who is also a right-wing commentator on social media, has been critical of the Mueller probe and sought to raise funds for Rick Gates and Michael Flynn, two former aides for U.S. President Donald Trump who pleaded guilty to charges brought against them by Mueller's team.

Trump denies any collusion and has repeatedly described Mueller's probe as a partisan "witch hunt."

Russia denies the allegations that it interfered in the election.