Last updated on .From the section Tennis

Serena Williams has called for American tennis player Tennys Sandgren to apologise for his controversial tweets.

The world number 97 deleted 18 months' worth of tweets after being questioned about his beliefs and denied he was a far-right sympathiser.

Following his Australian Open quarter-final on Wednesday, he accused the media of "demonising" and "propaganda".

"There is an entire group of people that deserves an apology," said Williams in a tweet external-link to Sandgren.

The 23-time Grand Slam winner added: "I can't look at my daughter and tell her I sat back and was quiet. No! she will know how to stand up for herself and others - through my example."

The tweet was accompanied by a fist emoji and a quote about apologising.

Earlier on Wednesday, the former world number one had tweeted external-link "turns channel" in an apparent swipe at Sandgren, during his defeat by South Korea's Chung Hyeon.

Sandgren, who said the media "dehumanise with pen and paper", was first asked about his social media presence following his fourth-round match on Monday, and denied supporting the US 'alt-right' movement, saying he merely found "some of the content interesting".

Despite insisting that whom he chose to follow on social media did not represent his views, Sandgren then deleted all but one of his Twitter postings.

Addressing a news conference following his match in Melbourne on Wednesday, he read a statement and then refused to take further questions on the subject.