The BuzzFeed website reports US Republican nominee Donald Trump made a cameo appearance in an explicit 2000 Playboy video.
In a short clip posted on the site, Trump is seen pouring a bottle of champagne on a Playboy-branded limo on a New York street, surrounded by a gaggle of women.
Clinton spokesman Nick Merrill said late on Friday, "There's been a lot of talk about sex tapes today and in a strange turn of events only one adult film has emerged today and its star is Donald Trump". Merrill said he not seen the video.
On Friday morning, Trump tweeted that former Miss Universe Alicia Machado, a Clinton supporter, was "disgusting," mentioning her "sex tape" - in an apparent reference to footage from a Spanish reality show in 2005 in which Machado was a contestant and appeared on camera in bed with a male contestant.
The images are grainy and do not include nudity, though Machado later acknowledged in media reports that she was having sex in the video.