Melbourne starts five-day coronavirus lockdown, no spectators at Australian Open

Victoria Police Protective Services Officers apprehend a man on the first day of a five-day lockdown implemented in the state of Victoria in Melbourne Australia

While there have only been three new local cases identified following thousands of tests since the lockdown was announced on Friday, Victoria's health officials said the tough curbs - forcing the state's six million-plus people to stay home for five days - were still needed.

Streets in downtown Melbourne, the state's capital, and its suburbs were nearly empty early Saturday, with people ordered to stay home for all but essential shopping, two hours of outdoor exercise, caregiving, or work that can not be done from home.

The state reverted to stage 4 restrictions on Friday midnight, with the 5-day lockdown aimed to act as a "circuit breaker" curbing the spread of the highly contagious United Kingdom variant of the virus responsible for the Holiday Inn outbreak.

Melbourne a year ago endured a 111-day lockdown, one of the strictest and longest in the world at the time, to stem a coronavirus outbreak which lead to more than 800 deaths.

"It is the advice to me that we must assume that there are further cases in the community than we have positive results for, and that it is moving at a velocity that has not been seen anywhere in our country over the course of these last 12 months", he said.

"That's, in essence, the reason for this five-day short, sharp lockdown".

The tournament, one of the sport's four Grand Slams, was delayed by three weeks and only went ahead after more than a 1,000 players and support staff underwent 14 days of quarantine. We will be able to smother this.

The departures terminal at Auckland International Airport. "They understand. They have been through a rigorous programme already", he added.

The function was also attended by a Holiday Inn hotel quarantine worker who didn't know she was infectious at the time, first testing positive on February 10.

"It will not be the same ... but it will be the most significant worldwide event with crowds that the world has seen in many, many months".

American star Serena Williams only learned of the new measures when she came off court after her 7-6 (7/5), 6-2 third-round win over Russia's Anastasia Potopova.

"It's not ideal - it's been really fun now with the crowd back".

"I think these last couple of days really do confirm for us that as hard as the call on Friday was, the advice that underpinned it was exactly the right call", he said. "Hopefully it will be all right".

Players also stayed in a "bubble" environment at last year's US Open in NY, which went ahead behind closed doors, and the delayed French Open. Wimbledon was cancelled for the first time since World War II.

"I'm happy that the tournament is going to go on".

The lockdown will quickly pose challenges on Friday, as high profile players including world number one Novak Djokovic, US Open champion Dominic Thiem and Australian showman Nick Kyrgios are due to play matches Friday night with the restrictions looming.

However, spectators may face a scramble to be home before Melbourne's lockdown starts at midnight, with play frequently continuing into the early hours.