Workers and residents in Sydney were ordered to stay home for a week on Friday, as authorities locked down several central areas of Australia's largest city to contain an outbreak of the highly contagious Delta variant of COVID-19.
Sixty-five COVID-19 cases have been reported so far in the flare-up linked to a limousine driver infected about two weeks ago when he transported an international flight crew from Sydney airport to a quarantine hotel.
But authorities have since identified scores of potential infection sites visited by thousands of people across central Sydney, including the city's main business district.
Authorities have been alarmed by instances of people passing on the virus during fleeting encounters in shops and then quickly infecting close family contacts.
Premier Gladys Berejiklian of New South Wales state, which includes Sydney, called it the "scariest period" since the pandemic broke out more than a year ago.
On Friday, she ordered anyone who lived or worked in four central Sydney neighborhoods to stay home for at least a week, only venturing out to purchase essential goods, obtain medical care, exercise or if they are unable to work from home.
The restrictions included central business district workers over fears that commuters were potentially spreading the virus into other parts of the city, Berejiklian said.
"We've done better than expected in terms of contact tracing and getting on top of all those links," she said.
"But what this does is make sure that we haven't missed any chains of community transmission."
An earlier ban on Sydneysiders leaving the city was also extended until next Friday, as traces of the virus were detected in sewage in the far-flung outback town of Bourke, about nine hours drive northwest of Sydney.
It was a dramatic development for a city that had returned to relative normality after months of recording very few local cases.
Australia Medical Association President Omar Khorshid chided New South Wales authorities for not taking tougher action, including locking down the entire Sydney metropolitan region, home to some 5 million people.
"The Delta virus is different; it is being transmitted far more easily," Khorshid told media in Canberra. "Sydney has not faced this before."
Korshid warned that although the economic impact of a lockdown was hard, a wider outbreak could be "catastrophic" for the whole country.
It is the latest in a string of snap "circuit-breaker" lockdowns across major cities around Australia, with most cases linked to returning travelers held in hotel quarantine.
Australia has been among the world's most successful countries in containing COVID-19, with more than 30,000 cases and 910 deaths in a population of about 25 million.