South Australia has imposed a range of new local COVID-19 restrictions in response to the growing number of virus cases around the country, after yesterday closing its borders to all states and territories except Victoria and Tasmania.
From midnight on Monday, masks will be mandatory in high-risk settings, including aged care facilities and hospitals and will be highly recommended on public transport.
A new density arrangement of one person to every two square metres will be enforced in cafes, pubs, restaurants and other venues while private gatherings will be limited to 150 people.
People consuming food and drink at indoor venues must be seated.
Premier Steven Marshall hoped the new measures would only be required for a week, but said the government was clamping down swiftly on the premise that the Delta variant of COVID-19 could spread rapidly:
"Given the nature of the rapid spread of the Delta variant we have no option but to take pre-emptive action to keep South Australians safe.
"We have to be very vigilant at the moment."
Victoria has reported no new local cases as it closed to Darwin and tightened border protocols with Brisbane and Perth over a Northern Territory mine outbreak.
Victoria confirmed zero locally acquired cases on Monday, with two in hotel quarantine.
It comes as Greater Darwin - including Darwin, Palmerston and Litchfield - was designated a red zone under Victoria's travel permit system from 8pm on Sunday.
Non-Victorian residents who have been in a red zone cannot enter the state, while residents can obtain a permit to return and self-isolate for 14 days.
The concern is linked to a COVID-19 outbreak at a Northern Territory mine, which has sparked a 48-hour lockdown of Darwin and its surrounding areas.
That threat has prompted Victoria's Chief Health Officer Brett Sutton to list Greater Brisbane, metropolitan Perth and its neighbouring Peel Region as orange zones from 1am on Monday.
Anyone coming from those areas can still enter Victoria with a permit, though must get tested and isolate until they receive a negative result.
Greater Sydney and surrounding regions, as well as Greater Darwin, are the only current places that Victoria has declared "red zones".
Prime Minister Scott Morrison has called a meeting of the national security committee of federal cabinet to discuss the situation.
He will also bring together state and territory leaders for a national cabinet meeting on Monday evening.
Treasurer Josh Frydenberg, who sits on the national security committee, said it would receive a briefing from Australia's chief medical officer:
"Bringing the leaders together and hearing the most up to date information is important to align the responses.
Mr Morrison is expected to push state and territory leaders to make vaccines mandatory for aged care workers.
Queensland is reintroducing restrictions after recording two new local cases of coronavirus.
Masks will be mandatory across large swathes of the Sunshine State, home visits will be capped at 30 guests and venues will need to adhere to a one person per square metre rule.
In the Northern Territory, the cluster arising from a central Australian mine has grown to six cases.
And in Western Australia, a woman who returned from Sydney has picked up the virus, prompting increased restrictions including indoor mask use.
WA also tightened its border for residents of Queensland, the NT and ACT, while Victoria added Darwin to its "red zone" list.
All states have locked out Sydney residents.
On Sunday, SA closed its border to Queensland, WA, the NT and the ACT effective immediately after previously locking out travellers from NSW.
Professor Spurrier said:
"At the moment we would say our community is a bit of a tinderbox and we are very concerned that if we get undetected cases it will take off very rapidly.
"This is an enormous wake-up call. This is the biggest threat in South Australia since the first wave.”