Elon Musk has denied reports that he had a brief affair with Google co-founder Sergey Brin's wife, Nicole Shanahan.

The Tesla and SpaceX boss said on Twitter there was "nothing romantic" between him and Ms Shanahan, adding that he and Mr Brin remain friends.

Mr Musk's tweets came after a Wall Street Journal (WSJ) report that cited unidentified sources saying he had engaged in a brief affair with Ms Shanahan.

The paper said the affair prompted Mr Brin to file for divorce from Ms Shanahan earlier this year and ended the tech billionaires' long friendship.

Musk replied to a tweet about the story on Twitter, adding that it was "total bs".

Tesla and Google, whose parent company is Alphabet Inc, did not immediately respond to requests for comment, and neither Mr Brin nor Ms Shanahan were available for immediate comment.

A lawyer for Mr Brin declined to comment to the WSJ, and Ms Shanahan didn't respond to requests from the paper for comment.

Google co-founder Sergey Brin and Nicole Shanahan

Mr Brin filed for divorce citing "irreconcilable differences," the Journal said, quoting records it said were filed in Santa Clara County Superior Court.

Reuters news agency was unable to determine independently whether divorce papers have been filed.

In its report, the WSJ also said Mr Brin instructed his advisers to sell personal investments in Mr Musk's companies after he came to know about the affair.

The paper said it wasn't able to determine how large those investments were, nor whether any sales were made.