New South Wales has recorded 112 new community cases of Covid-19, 34 of which were infectious in the community.

The new cases take Sydney's outbreak to a total of 678 infections.

There are currently 63 cases admitted to hospital, with 18 people in intensive care, four of whom require ventilation.

There is now little hope that the Greater Sydney lockdown will end as planned at 11.59pm on July 16, with NSW Premier Gladys Berejiklian saying yesterday it was "highly unlikely at this stage" that restrictions will ease.

Berejiklian said today the number of people out in the community while infectious needs to drop dramatically.

"It is critical, that is something all of us have a role to play in. All of us have to make sure that if anyone has symptoms, get tested and stay at home," she said. "Don't go to work, and under no circumstances should anybody be visiting another household."

Current lockdown insufficient - experts

There are growing calls for NSW to tighten restrictions as case numbers continue to rise despite parts of the state entering a third week of lockdown.

The current rules for Sydneysiders mean a person can only leave home for four reasons: to get food and essential items once a day, for work, for exercise or to seek medical care or a vaccination.

Face masks are mandatory in all indoor settings including public transport and funerals have been capped at 10 people. All schools have been closed to face-to-face learning.

Under the current rules, pubs, clubs, restaurants and cafes are open for takeaway, but places of worship, hairdressers, auction houses, betting agencies, markets, massage parlours, nightclubs and swimming pools are all closed with no exceptions.

Burnet Institute's head of public health, Professor Mark Stoove, said NSW's numbers prove the current restrictions aren't enough to get the state's outbreak under control.

"I think numbers speak for themselves. In Victoria it took 14 days for stage four lockdowns to start having an impact on numbers," he told 7 News, pointing out Sydney's lockdown has been going for 17 days.

"I don't think the current lockdown measures are sufficient, so an extension, but also tightening of lockdown rules is necessary.

Stoove said NSW needed to look at the type of measures that were in place across Victoria during their lockdown, such as curfews and travel limits.

"There were 5km limits, retail was closed, we had curfews at night. It was as much limiting of movement as possible," he said.

Adjunct Professor at UNSW Bill Bowtell agreed the current rules were insufficient, telling ABC News that the "big retailers that are not providing essential goods and services should not be open".

Professor of Epidemiology at the University of South Australia, Adrian Esterman, said maintaining the same restrictions will only result in cases continuing to climb.

"I can't see why [numbers] will go down with a further week of lockdown, unless there is further intervention."

He suggested "tightening the definition of an essential worker, or introducing a curfew, and somehow getting better compliance with the regulations".

Epidemiologist and World Health Organisation (WHO) adviser Professor Mary-Louise McLaws said NSW may need a month of hard lockdown restrictions in order to defeat the current outbreak.

"I suggest that we're in a lockdown for at least another three to four weeks, and then looking at whether or not you've got this under control, you need another couple of weeks to see that you've got zero," she told ABC News.

The Federal Government launched a new advertising campaign on Sunday encouraging people to "arm yourself" against Covid-19 by getting jabbed, though vaccines are yet to be offered to most under-40s.

Federal chief medical officer Paul Kelly said other "graphic" adverts would be broadcast in Sydney urging people to follow stay-at-home orders, as police step up enforcement amid reports that flouting of the rules was widespread.

Australia has recorded just over 31,000 cases of Covid-19 and 911 deaths in a population of about 25 million.