Between 500 and 600 Australian Open players, officials and support staff will go into isolation after a worker at one of the event's quarantine hotels tested positive for coronavirus.

Thursday's play at the six warm-up events at Melbourne Park is set to be affected by the move, says Victoria Premier Daniel Andrews.

But Andrews said: "At this stage there is no impact on the tournament proper."

Players will be free to return to competing after a negative test.

The Australian Open, which was pushed back by three weeks to enable players to quarantine, starts on Monday.

A 26-year-old man has tested positive for Covid-19 - believed to be the UK strain of the virus - after working at the Grand Hyatt hotel in Melbourne's Central Business District, Andrews said.

This was one of the hotels where some of the 1,000 players, officials and support staff stayed to complete a 14-day quarantine period on their arrival in Australia.

Andrews said the 500-600 people there for the Australian Open were deemed to be "casual contacts" of the man.

"This is one case, there is no need for people to be panicked or alarmed," said Andrews, who announced the state of Victoria would return to some restrictions including masks to be worn indoors.

"We have proved as a state very successful in managing these sort of outbreaks and issues."

Asked about the Australian Open, he said: "We have one case and the decision has been made: the event will proceed next week."