Fed-up Federer says multilingual line judge landed him with a $3,000 fine for SWEARING during Australian Open quarter-finals

Swiss tennis superstar Roger Federer was left frustrated and out of pocket after being slapped with a $3,000 fine for swearing in a multilingual rant during his quarter-final win over Tennys Sandgren.

Federer was handed a code violation during the match after a lineswoman reported the Swiss star's verbal obscenity to umpire Marijana Veljovic during the third set of the match.

While Federer admitted he had indeed used cuss words on the court, he revealed that he did so in "a mix" of languages, and said the way he was handed his on-court warning left a sour taste in his mouth.

Speaking about the line judge who reported his swearing to the umpire, Federer said: "Clearly she speaks mixed. Didn't know that. Next time I got to check the (language skills of the) lines-people.

"Honestly, to be frustrated at one point... I think it's normal.

"I found it a bit tough. It's not like I'm known to throw around words and whatever. It's not like the whole stadium heard it either."

Despite his on-court annoyance, Federer managed to keep his composure and save seven match points before eventually defeatint Sandgren to book his place in Thursday's semi-final against defending Australian Open champion Novak Djokovic.