Victorian Premier Daniel Andrews has announced a state of disaster has been declared from 6pm on Sunday in addition to the state of emergency.
Andrews announced 671 new cases of Covid-19 and seven deaths along with the new stage four restrictions.
Metropolitan Melbourne has been put under a curfew from 8pm tonight. This will run from 8pm to 5am every day.
"The only reason to be out of your home between the hours of 8pm and 5am is to get care, to give care, or to go to and from work or be at work. We can no longer have people visiting others. We can no longer have people simply out and about for no good reason whatsoever," Andrews said.
Recreational activity has been banned and exercise limited to one hour each day.
Regional Victoria will also go into stage 3 restrictions from midnight on Wednesday.
The restrictions will apply for six weeks.
"I have a new series of stage four restrictions to announce," Andrews said.
"There will be additional limits to the four reasons to leave home. You will no longer be able to leave home and go any further away from your home than a 5km radius.
"You will not be able to be at any point more than 5km away from your home for the purposes of shopping for what you need.
"Only one person will be able to go shopping once per day and they will need to secure the goods and services that you need within a 5km radius."
Andrews said "recreational" activity is no longer allowed in metropolitan Melbourne.
He said this means no more than two people exercising, no more than 5km from home.
"You will be able to have one hour of exercise, no further than 5km from your home," he said.
"That means it's fresh air. It's a jog. It's a walk. It's in your local neighbourhood. It is staying close to home or in your home.
"And there will no longer be able to be groups any bigger than two, regardless of whether they're from your family or someone else."
He said daily exercise is an opportunity to do "just that" and not an opportunity "to live our lives as if this pandemic was not real, and was not literally the biggest challenge we've perhaps ever faced".
Andrews said: "Ultimately, all of these changes are about limiting movement."
Andrews said regional Victoria will move to stage 3 restrictions.
"It is with some regret but given the significant community transmission and the growing case numbers, and the fact we need to stay ahead of this in regional Victoria, from midnight next Wednesday, regional Victoria will move to stage three restrictions," he said.
"That's stay at home, except for the four reasons to leave. That will mean restaurants, cafes, bars, gyms, a whole range of other settings will need to close from midnight next Wednesday.
"That is not the position we wanted to be in but we cannot have a situation where this continues to grow and grow in regional Victoria and then we have a situation where as we are perhaps bringing stability and reduced numbers to metropolitan Melbourne, we have a problem that is even larger and spread right across regional Victoria.
"We just can't have that. So those changes will come into effect from midnight Wednesday night. That gives all of those who are most affected, that gives them time. The time will be important to businesses who will need to move to a home delivery or takeaway only model."
Schools essentially shut down
Andrews confirmed, among the other restrictions he announced, all Victorian schools will be essentially shut down.
From Wednesday, schools will move to flexible and remote learning for all students in all schools right across the state.
Year 11 and 12s in metropolitan Melbourne, who had returned to the classroom, will go back to working from home.
Special schools will remain open for those who really need to be in those settings, the premier added.
Tomorrow will be a normal day of school, Tuesday will be a pupil-free day and then all Victorian students will transition to learning from home on Wednesday.
"The children, the students of parents who are working, they will be able to go to school and be supervised but it will really only be those that are absolutely necessary to do so," Andrews said.
"We'll be reducing the total amount of students that are at school and therefore the total amount of movement."
Andrews said he expected there to be larger numbers of students at school in regional Victoria because their parents will be working away from home.
"That economy in the regions will be functioning at a higher level and won't be limiting the number of students who can come and be supervised because they simply can't be supervised at home," he said.
"I want to make the point that vulnerable children, children that really do need that in school experience, they will get that. They will be supported."
Andrews said the rapid shutdown of schools was a "difficult decision".
"But if you think about it from regional Victoria, that's more than 100,000 people who are not going to be moving around regional Victoria who otherwise would be," he added.
"These are tough choices but they are the decisions that I've taken because they're the decisions that will keep us safe and get us past this."
Andrews said he didn't want to "reflect negatively on fellow Victorians" but "we have seen some behaviour that's just not on".
"I don't think it's too much to call that out," Andrews told reporters.
The premier said police and the ADF would be ramping up its enforcement of the lockdown and it was time for people to "change their behaviour".
"There's a number of different ways in which we can do that. I have gone to the notion of additional ADF and police and public health teams that will be doing more and more door knocking," Andrews said.
"That just means it's much more likely that if you take the gamble to not be where you should be, that you will be found out and fined.
"We've always reserved the right for those who are the most flagrant breaches of these rules, breakers of these rules, to take it through the courts and have the much bigger fine, not the smaller on the spot fine.
"$1652 is not a small amount of money and you can be fined multiple times."
'Six weeks should be enough'
Victoria's chief health officer Dr Brett Sutton said he's optimistic a six-week lockdown should be enough to stop the state's coronavirus epidemic.
"It is entirely on everyone in Victoria to make sure (six weeks) is enough," Sutton said.
"If we do the things we know work to test, to isolate and to have our close contacts quarantined, and to follow all of these directions that we're laying out today and tomorrow, six weeks should be enough.
"But it has to have everyone's co-operation and understanding.
"There's no question it's challenging for people. And there's no question that it's going to be impactful. But they're absolutely necessary things."
Sutton said there was plenty of proof stage 3 restrictions had helped Victoria but there was still more work to be done.
"The stage three restrictions show that you can shift things but we have come up against some really significant challenges. People who aren't aware. People who aren't following the rules.
"Workplaces are obliging their staff to turn up when they're unwell, those things need to change.
"All of these measures, including the compliance and enforcement in workplace settings to make sure workplaces are doing the right thing by their employees, for everyone's benefit, that all needs to come into place."
Younger people make up more than half of Victoria's coronavirus cases, chief health officer Sutton confirmed today.
"Young people, 15 to 40 years of age, make up over 50 per cent of our total cases. Something like 53 per cent," he said.
"In part, our intensive care units have been protected by virtue of younger people making up such a significant proportion. But the huge numbers that we're seeing week in, week out will still show up in our health system.
"We need to see those numbers through the eyes of our healthcare workers and the kind of awful fear that they have about what it means for people presenting to hospital.
"We need to get on top of the numbers regardless of the age groups that are affected.
"Younger people are overrepresented in some ways and our intensive care units have been protected by the relatively fewer numbers of people in their 60s and 70s who have contracted the virus."
Seven deaths reported today
The reported deaths of Covid-19 today are three women in their 70s, two women in their 80s, one man in his 90s and one woman in her 90s.
He said six of the seven cases are connected to aged care.
Andrews said he wanted to highlight the number of mystery cases.
"That is, in many respects, the most important number," he said.
"As of today – and this number will only grow because there are 598 cases that are being investigated by our public health team – but as of today, from work that's been undertaken in recent days, we have 760, 760 mystery cases.
"They are active cases where we can't trace back the source of that person's infection. Either who they got it from or where or how.
"Those mysteries, that community transmission is in many respects our biggest challenge and the reason why we need to move to a different set of rules."
12 new cases in NSW
More than 22,400 tests were conducted on Saturday in New South Wales, with 12 new cases confirmed on Sunday.
Of the new cases, one was a traveller in hotel quarantine. Three cases had been to the Apollo restaurant in Potts Point on July 25. Two cases attended the Mounties club in Mount Pritchard on July 23.
Five of the 12 cases are close contacts of known cases, and one case is locally acquired with no known source identified.
NSW chief health officer Dr Kerry Chant said that person was a childcare worker who attended the Advanced Early Learning Centre in Merrylands while infectious between July 27-29.
"A second case has been reported this morning in another staff member at that centre," Chant said.
"The centre is currently closed for cleaning close contact tracing is underway."
In Western Australia, one new case of Covid-19 has been recorded.
"The Department of Health has reported one new case of Covid-19 in Western Australia overnight, a man in his 30s who returned from overseas. He is in hotel quarantine," WA Health said in a statement on Sunday afternoon.
"This brings the total case count to 641."
The department said the total is reduced from Saturday's figure of 668 "because historical cases diagnosed through a blood test and indicative of infection in the past are no longer being reported in the daily report or in overall figures".
"This change has been made to bring WA's reporting closer into line with other Australian jurisdictions," it said.
There have been two new cases of Covid-19 recorded in South Australia.
One is a teenage girl who flew from Melbourne on a Jetstar flight, SA chief public health officer Professor Nicola Spurrier said on Sunday.
Seven close contacts have been ordered to quarantine.
The second case is a woman in her 20s considered a close contact of a known case.
A woman with Covid-19 has attended a school in SA however it is not yet clear which school.