Tens of thousands of people will be confined to metropolitan Sydney under new rules as states harden borders with NSW after 13 new COVID-19 cases were diagnosed following a "super-spreader event".
Authorities moved quickly on Wednesday to suppress the rapid spread of the highly infectious Delta variant after the so-called Bondi cluster blew out to 31.
Premier Gladys Berejiklian imposed immediate restrictions for Greater Sydney, the Central Coast, Blue Mountains, Wollongong and Shellharbour.
"Please abandon non-essential activities, please don't attend social gatherings unless you absolutely must," the premier said on Wednesday.
Later, during parliament's question time the premier warned the government "will not hesitate to go further and harder if we have to".
Other states responded to the development swiftly, slamming the borders shut immediately or imposing strict travel limits.
The outbreak has escalated dramatically since an unvaccinated Sydney airport limousine driver last week tested positive to the highly infectious Delta variant, which quickly spread at Bondi Junction's busy Westfield shopping centre.
The new restrictions mean that from Wednesday people who live or work in the City of Sydney, Waverley, Randwick, Canada Bay, Inner West, Bayside, and Woollahra local government areas cannot travel outside the metropolitan area unless it's absolutely essential.
The metro area is defined as the Hawkesbury/Nepean River in the north/north west and the outer boundaries of the City of Penrith, Camden Council, the City of Campbelltown and Sutherland Shire.
"We don't want the virus to spread to the regions," Ms Berejiklian said.
NSW recorded 10 locally acquired cases to 8pm on Tuesday, seven of which were already announced.
An additional 13 cases were reported after 8pm, which will be counted in Thursday's official tally. Four of these cases are currently unlinked to existing cases.
Overall, there have been 16 new cases taking the total number of infections to 31, from 21 on Tuesday.
Under the new restrictions, household visitors are limited to five people, including children and masks are now compulsory in non-residential indoor settings - including workplaces - and at outdoor events.
Masks must also be worn to gym classes, which are limited to 20 people.
More than 44,000 tests were completed in the 24 hours to 8pm on Tuesday.
Eight of the 13 cases confirmed overnight had attended a birthday party attended by about 30 people in West Hoxton on Saturday, which NSW Chief Health Officer Kerry Chant described as a "super spreader event".
An asymptomatic worker from Bondi Junction went to the party as did a father and a daughter.
The child then went to her childcare centre 60km southwest of Sydney's CBD on Monday.
Little Zak's Academy Narellan Vale confirmed it had been closed for deep cleaning.
Dr Chant warned there were people "unknowingly" infected in the community and "a very real and present danger" ... right across Sydney".
"We need to all take this seriously."
Meanwhile, three NSW Nationals MPs who all attended a Paddington pizzeria on Monday night are among those isolating.
Joh Bailey's hairdressing salon in Double Bay - which is famous for its rich and famous clientele - was also added to the growing list of hot spots on Wednesday.
The spike in infections is a blow for families with school holiday plans now in tatters as states harden their borders just two days before public schools break for two weeks.
WA closed its border to anyone but exempt travellers from NSW who had been in the state since June 11 with arrivals needing to quarantine for 14 days and have a mandatory test.
Tasmania has banned travellers who aren't Tasmanian residents from the seven declared hotspots.
SA closed has closed its border with NSW "effective immediately", excluding a 100km buffer zone for cross border communities and allowing for SA residents and essential workers.
From Thursday Queensland will close its border to people from the same seven declared hotspots.
Victoria had already banned people from the "hot zones" and mandated that Victorians returning home from those areas must quarantine for a fortnight.
New Zealand has paused its travel bubble with NSW after a person infected with the virus flew from Sydney to New Zealand and back.
NSW Health issued an alert for passengers travelling on Qantas flight QF163 on Friday night to Wellington, and anyone who flew on Monday morning on Air New Zealand flight NZ247 from Wellington to Sydney.