Nick Kyrgios apologises after on-court comment to Stan Wawrinka about his girlfriend causes outrage

Tennis star Nick Kyrgios has apologised after he sparked outrage when he caught making comments about his opponent's girlfriend during a match.

A courtside microphone at the Montreal Masters picked up Kyrgios telling Australian and French Open champion Stan Wawrinka that another player, Thanasi Kokkinakis, had slept with his girlfriend.

"Kokkinakis b****d your girlfriend - sorry to tell you that mate,” the 20-year-old is heard saying.

Kyrgios made the apology using his Facebook page.

Wawrinka - who retired through injury in the third set of the match - had posted a series of tweets condemning the comments and urged the Association of Tennis Professionals (ATP) to take a stand.

His coach Magnus Norman also hit out at Kyrgios's comments.

Kyrgios was initially unapologetic, saying in a post-match interview: “He was getting a bit lippy with me. Kind of in the heat of the moment. I don’t know. I just said it."

Kyrgios has been embroiled in controversy during his short career.

He was accused of not trying, or "tanking", during his defeat by Richard Gasquet at Wimbledon earlier this year.

The Association of Tennis Professions (ATP), meanwhile, have decided to fine Kyrgios for his in-game jibe. In a statement released this afternoon, they said:

Details of the fine are not being made public until after Kyrgios has been notified.