"I offer you most profound apologies," he told Colombian journalist Julieth Gonzalez Theran in a video call that was shown by broadcaster Deutsche Welle.
"I acted carelessly and did not think that I would cause you confusion and shock," added the fan, who declined to give his name.
Theran was reporting from the Russian city of Saransk when the man appeared suddenly, one hand grabbing her arm and the other her breast while kissing her on the cheek.
His abrupt action sparked condemnation of sexual harassment from the German international channel, whose clip of the incident went viral online.
The Russian man said he had placed a bet with a friend that he could kiss the reporter on the cheek, and had waited for her to go on-air before springing on her.
Theran said she appreciated his apology and voiced her determination to move on from the episode.
"I refuse to be a victim, I just want to continue with my job," she said.
The assault came at a time when the online #MeToo movement against sexual misconduct has made waves around the world, prompting victims to come forward to report harassment, including by leading figures in industry and the arts.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.