New South Wales has recorded 415 new local cases of Covid-19 and four new deaths.
The new deaths take the death toll in the latest outbreak to 48 and include a woman in her 50s, a woman in her 70s, a woman in her 80s and a man in his 80s.
Of the new cases, 42 cases were infectious in the community, and the isolation status of 273 cases remains under investigation.
There have now been 7,745 cases linked to the latest Sydney outbreak since it began in mid-June.
NSW's pandemic response was at a fork in the road, chief medical officer Dr Kerry Chant said.
"We have to decide what path we will choose," she said. "The path I want is one where I see declining case numbers and increasing vaccination uptake."
NSW suffered its worst day of the pandemic yesterday with 466 local cases and four deaths, prompting Premier Gladys Berejiklian to unveil a police operation to enforce lockdown compliance across Sydney.
The entire state was later plunged into a seven-day lockdown, which was announced suddenly via social media, giving regional residents little time to prepare and sparking fury online. All 7.95 million NSW residents in are now in lockdown.
Under the stay-at-home orders across the state, anyone who leaves their home will need to have a reasonable excuse. They also cannot have visitors in their home from outside their household. All hospitality venues are closed to the public. Most retail premises are required to close.
People who leave their home are required to carry a mask with them at all times. They must be worn when working outdoors, by all school staff, by all people in outdoor markets, outdoor shopping strips, and in an outdoor queues.
The lockdown compliance operation will see police and Australian Defence Force officers enforce the state's restrictions after officials blamed rule-breaking for the continued growth of the outbreak.
NSW now has 1400 Highway Patrol officers across the state working solely on enforcing compliance. Drivers have been told to expect more roadblocks, where police will be checking identification and proof of address.
"These are some of the strongest laws, with some of the strongest police action coming. I am not apologetic," NSW Police Commissioner Mick Fuller said on Saturday.
"Please don't write in and complain to me. We have given ample warnings and cautions, and that time has gone."
According to Fuller, movement within the Greater Sydney region still remains too high, and "getting compliance from some members of the community" has been difficult.
In reminding residents of the lockdown rules and the harsh new fines for breaching state health orders, Berejiklian said "the buck stops with me".
"For a long time, nearly a year and a half, we were different to the rest of the world," she said.
"And now, we are not different from the rest of the world. The Delta strain is diabolical, and we have to accept and be real about that."
Victoria has recorded 25 new local cases of Covid-19, with all but four of those cases linked to known outbreaks.
Only 12 of the new cases had been in isolation throughout their infectious period.
Health authorities remain concerned about a number of mystery cases across the city as investigations continue into the source of twelve infections.
"We are very concerned about what we're seeing across Melbourne," Victoria's coronavirus Response Deputy Secretary Kate Matson said on Saturday.
Victorian Premier Daniel Andrews said today the number of mystery cases in the state meant case numbers would "continue to grow".
He said if the state were to reopen now, Victoria would soon end up like NSW.
"I know [the lockdown is] difficult, but so is being on a tube to breathe," he said. "The consequences are very serious."
Victoria's list of exposure sites has ballooned to nearly 500, many of them in Melbourne's west but a number also in inner Melbourne.
There are now more than 14,000 primary close contacts in isolation.
Melbourne's lockdown, scheduled to end on Thursday, is very likely to be extended into a third week.
ACT have recorded another two cases of Covid-19 today, bringing the total number in the outbreak to nine cases.
The Australian capital entered a snap seven-day lockdown earlier this week after a confirmed Covid-19 case from an unknown source was recorded.
More than 3,290 Covid-19 tests were conducted in the ACT yesterday, including at a pop-up centre at a local school, prompted by a 14-year-old student who tested positive.
The ACT lockdown, like Melbourne's, is scheduled to end on Thursday.
Queensland has recorded no new locally acquired Covid-19 cases on Sunday as the state continues to recover from the Indooroopilly cluster.
Premier Annastacia Palaszczuk said it was an "absolutely perfect way to start a Sunday" but warned their could still be cases emerge from the Indooroopilly school cluster.
"We are not out of the woods yet so if you have any symptoms, however mild, please go and get a test, that is absolutely critical," she said.
One new case was recorded in hotel quarantine on Sunday.
It comes as Queensland's chief health officer Jeannette Young tightened the border zone rules overnight as a statewide NSW lockdown was enforced.
NSW border zone residents can now only enter Queensland for obtaining essential goods and services that can't reasonably be obtained in NSW.
"The situation in NSW continues to be very concerning," Young said.
"Given the escalation of local restrictions, we have no choice but to put in place a tighter border situation to protect Queenslanders."