Rogers Cup: Kyrgios tells Wawrinka someone slept with his girlfriend

Stan Wawrinka of Switzerland goes up to the net as he returns to Nick Kyrgios of Australia during second round of play at the Rogers Cup tennis tournament Wednesday August 12, 2015 in Montreal. (Paul Chiasson / The Canadian Press)

MONTREAL -- French Open champion Stan Wawrinka urged tennis authorities on Thursday to take action against Nick Kyrgios for an "unacceptable" comment during a match at the Rogers Cup.

Wawrinka wrote on his Twitter account that the Australian's words were "not only unacceptable but also beyond belief."

A courtside microphone picked up the 20-year-old Kyrgios saying that Australian player Thanasi Kokkinakis had slept with a player who is reportedly Wawrinka's girlfriend.

"There is no need for this kind of behaviour on or off the court and I hope the governing body of this sport does not stand for this," the 30-year-old Wawrinka wrote on Twitter.

Wawrinka, ranked fifth in the world, announced in April that he had separated from his wife, with whom he has a daughter.

Wawrinka has since been linked with 19-year-old Donna Vekic of Croatia, who is ranked 127th.

Vekic played mixed doubles with Kokkinakis, also 19 and ranked No. 76, at the 2014 Australian Open as a wild-card entry.

Kyrgios beat Wawrinka on Wednesday when the Swiss retired with a lower-back injury while trailing 4-0 in the third set.

In a post-match interview on court, Kyrgios said Wawrinka had provoked him.

"He was getting a bit lippy at me so, I don't know, it's just in-the-moment sort of stuff," Kyrgios said. "I don't really know, I just said it."