Australian Open tennis players have begun to leave hotel quarantine after completing their 14-day isolation, about a week before the event starts.

By Sunday, about 500 players will have been released from hotels in Melbourne and Adelaide, organisers said.

High-profile stars Novak Djokovic, Rafael Nadal and Serena Williams were among those allowed out on Friday.

Players have quarantined because of the Australian government's Covid-19 rules for anyone entering the country.

In early January, more than 1,700 players, staff and others tied to the Grand Slam were flown into Australia on chartered flights. The tournament begins on 8 February.

Unlike other returning travellers who stay full-time in hotel rooms, players were allowed out of their rooms for five hours a day to practice on court and exercise.

A smaller group of 72 players were fully confined to their rooms in Melbourne, however, after coronavirus cases were discovered on their flights.

Eight cases have been linked to the event so far, including Spanish tennis player Paula Badosa.

The quarantine policy had prompted criticism from several players who were concerned about how it would impact their preparation.

US tennis player Tennys Sandgren and Georgian player Oksana Kalashnikova continued this criticism on Thursday, after saying they had learned their confinement would be extended by another day.

"It's also another day we can't practice," Sandgren wrote on social media.

He said he would have only three days of practice outside the room before playing a competitive match.

Melbourne endured one of the world's longest lockdowns last year and many locals have concerns about the potential Covid risk posed by the tournament.

Some players have acknowledged what Melburnians went through last year, and expressed thanks to Australian authorities for facilitating the event.

"Conditions were great for us, considering the circumstances," said Djokovic in Adelaide on Friday.

Earlier this month, the men's world number one lobbied Tennis Australia for better conditions for players in hard lockdown.

On Friday, he said he had gone for a walk in a park: "Just putting feet on the ground... just having the space, I think, that's what we all kind of missed."

He initially missed the first half of an exhibition match in Adelaide, after he pulled out citing blisters on his hands. However, he later returned to play the second set. The match had been part of a deal to allow him to quarantine in Adelaide.

At the same press briefing earlier, Williams said she was "so glad" her quarantine had ended.

"To be in a room with a three-year-old and being her best friend is definitely difficult especially after training and working out... it's like, oh my gosh, it never ends," she joked to reporters.

"We had a calendar in our room and every day we marked an X on the day that went by and a big circle on the quarantine ending day."