Serena breaks down at press conference

Serena Williams broke down in tears before cutting short her post-match news conference after losing 6-3, 6-4 to Naomi Osaka in the Australian Open semi-finals on Thursday.

The defeat ended Williams's bid for a record-equalling 24th Grand Slam title.

"The difference today was errors," Williams said in her news conference.

"Honestly, it was opportunities where I could have won. I could have been up 5-Love. I just made so many errors. I had so many opportunities, ...it was just...I made too many mistakes there and easy mistakes," said the American.

"Not like...I was on the run or anything. They were just easy, easy mistakes. 

"It was a big error day for me today," the 39-year-old told reporters after the match at Rod Laver Arena.

She paused while walking off as the centre court crowd gave her a standing ovation. She put her hand on her heart, smiled and waved.

"The Aussie crowd is so amazing, so it was nice to see," Williams, sporting a "Queen" necklace, told reporters.

Williams was asked whether the gesture was meant as a final farewell to Melbourne Park, where she holds a record seven titles in the professional era.

"I don't know, if I ever say farewell I wouldn't tell anyone, so...." she responded.

Asked if it was just a bad day at the office, Williams said: "I don't know. I'm done," before leaving the room in tears.

Seven-time Grand Slam champion Mats Wilander said Williams' tears were due to her disappointment at the way she played and not a sign that she was making her last appearance at Melbourne Park.

"No (it’s not the end for Serena). I think we see those tears because I think she was disappointed in the way she played," said Eurosport pundit Wilander, a three-time winner at Melbourne Park.

"For her this is a bigger loss, because she is moving better, she is playing better and she is still not really close to Osaka and I feel that’s where the emotions start -- she's probably thinking, what do I need to do now?"