A Spanish tennis player has apologised after slamming quarantine rules at the Australian Open, days before testing positive for Covid-19.

World number 67 Paula Badosa said she understood "the sad situation", adding: "Sorry guys."

The 23-year-old was among tennis stars who complained about their confinement ahead of the tournament, which was delayed by three weeks due to the pandemic.

Three of 17 charter flights carrying the players into the largely virus-free country reported positive cases, meaning the 72 players aboard -- including Badosa -- were limited to their hotel rooms for 14 days.

Players on the other flights were allowed out for five hours a day, to train under strict conditions.

Many participants, including men's world number one Novak Djokovic, who was not in the full-quarantine group, took issue with the quarantine arrangements.

The players' complaints drew an unsympathetic reaction from Australian media, politicians and citizens online, many of whom angrily defended the strict isolation measures, especially as Melbourne only came out of a four-month lockdown in October.

This week, in a tweet reported by Australian media that has since been deleted, Badosa said that, according to her understanding of the rules, only people sitting near a positive case would be isolated -- "Not the whole plane."

"Not fair to change the rules at the last moment," she added. "And to have to stay in a room with no windows and no air."

But on Thursday, seven days into her quarantine, Badosa became the first female player on the tournament's roster to announce a positive test.

"I have some bad news," she tweeted. "I received a positive Covid-19 test. I'm feeling unwell and have symptoms."

After some online observers noted the irony of her earlier complaints, Badosa posted: "Health will always comes first & I feel grateful for being in Australia. Quarantine & preventive measures are pivotal right now.

"I talked about rules that changed overnight but I understand the sad situation we are living. Sorry guys. Stay safe."