NSW reported 642 new locally acquired cases of COVID-19 - the third consecutive day daily infections have exceeded 600 - and four deaths.

"We're doing everything we can, we're throwing everything at this ... It is time for all of us to bunker down and take this as seriously as we can," the premier said on Friday.

Stay-at-home orders will now apply in Sydney until at least September 30, Ms Berejiklian announced on Friday. The regions are locked down until at least August 28.

From Monday, mask-wearing will be mandatory for all people in NSW when outdoors, except when exercising.

Stricter rules will apply in the 12 hotspot local government areas in western and southwest Sydney, including a curfew from 9pm to 5am.

Ms Berejiklian and Chief Health Officer Kerry Chant both conceded evidence on the efficacy of curfews was "mixed".

"I do not want us to have to look back and say we did not try, we did not put everything into it," Ms Berejiklian said.

Residents in those council areas are from Monday limited to one hour of outdoor exercise per day.

Hardware stores like Bunnings, office supply stores and other retail premises must close there except for click-and-collect.

All exams and education activities in those areas must move online, except the HSC.

Workers living in the LGAs but working elsewhere will only be able to go to work if they've been vaccinated or have taken a rapid antigen test on their worksite.

Workers from those LGAs will also need a permit from Service NSW to say they are an authorised worker and cannot work from home, as will people working in the relevant LGAs.

A permit system will from Saturday also come into force for people travelling between Greater Sydney and regional NSW.

Furthermore, the government will again give NSW Police greater powers to enforce compliance.

Commissioner Mick Fuller will be able to lock down apartment blocks while NSW Health assesses COVID risk - before anyone even tests positive.

People who enter LGAs of concern without a reasonable excuse will face fines of $1000 and an order to isolate at home for two weeks.

Despite the harsh new rules, Dr Chant said she expected case numbers to continue to increase.

Whether they eventually start to fall "is in the hands of all of us", she said.

"What we need to do is break the cycle of transmission, and that is complex because of the large family sizes and seeding into workplaces," Dr Chant said.

COVID-19 vaccinations for all NSW healthcare workers will also be mandated by the end of next month, and for childcare workers and disability support workers in the council areas of concern by August 30.

There were 644 new local cases recorded in the 24 hours to 8pm on Thursday, but two were acquired in the ACT and are isolating in southern NSW.

Of the four deaths in the 24-hour reporting period, one was a man in his 70s, one was a man in his 80s and two were women in their 80s.

One of the women in her 80s was a resident of the Wyoming Aged Care facility in Summer Hill and was not vaccinated. The other three people had received one vaccine dose.

The virus continues to predominantly infect young people, with 80 kids under 10 testing positive in the 24-hour period. Some 107 of the new cases were aged between 10 and 19 and 162 are in their 20s.

Australian Associated Press