NSW has recorded two new cases of Covid-19 as Sydney's eastern suburbs outbreak continues to grow.
The two cases were diagnosed after the 8pm reporting cut-off and will be included in tomorrow's numbers.
One is a man in his 30s from Sydney's eastern suburbs. He is a close contact of a previously reported case and has been in isolation.
The other is a woman in her 50s who is a close contact of a previously reported case. She lives in Sydney's northern suburbs and has also been isolating, NSW Health said.
The two new cases take the Bondi cluster to 11.
Four new cases were announced on Sunday. Two of those were recorded before the 8pm reporting cut-off, and the other two were included in yesterday's numbers.
Earlier, epidemiologist and World Health Organisation adviser Professor Mary-Louise McLaws told ABC radio that NSW needs to take this outbreak of the Delta variant "very seriously".
She said if there are any more than "one or two" new locally acquired cases then officials should seriously consider imposing a three-day lockdown.
"If the numbers go up any further we should really be thinking about a three-day lockdown," she said.
McLaws also said masks should be made mandatory in all public areas for Greater Sydney.
Premier won't rule out tougher restrictions
Speaking on Sunday, Premier Gladys Berejiklian said while authorities don't want to extend restrictions, they will if they have to.
"At this stage, we didn't want to make the decision to have compulsory mask-wearing across all greater Sydney, but if the situation changes overnight, that is an option we will have to consider," she said.
"The strongest message I want to send our community is we worked on the basis of trust, that we won't impose any burdens on communities unless we absolutely have to. At this stage, given the number of cases and the risk, we feel [what] we are doing is appropriate."
Berejiklian said the next few days would be critical for NSW, saying any further restrictions "will depend on what cases, if any, emerge in the next few days".
She urged people with even the slightest symptoms to get tested so authorities can track down any underlying chains of transmission.
"We know everybody is tired. All of us are. We have to keep doing the right thing until we get the vaccine to majority of our population. This is what we have to live with.
"What we've asked people to do today is as far as we will go, but I will say that if cases continue to emerge in the community we will need to consider going further, but I hope that isn't the case. I hope in the next few days things settle down, and we don't have to go further."
A number of changes to mask restrictions kicked in at 4pm on Sunday, including the requirement for masks on public transport being extended to include Wollongong and Shellharbour.
Previously this restriction only applied to Greater Sydney and the Blue Mountains but was extended after a confirmed case spent time in Wollongong.
Masks are now also mandatory in indoor premises for certain local government areas, including Bayside, Canada Bay, Sydney, Randwick, Inner West, Waverley and Woollahra.
These indoor venues include retail and business premises that provides goods and services to the public, gaming rooms, entertainment facilities, places of worship, residential aged care facilities (but not for residents), and for front end staff at hospitality venues.
Penalties of $200 apply for defying mask restrictions.
Authorities racing to avoid 'superspreader event'
The new mask mandates were brought in to help avoid a "superspreader event" that could see cases explode across Sydney and surrounding areas.
"As we heard in previous days, on a few occasions it has been a fleeting exchange [that has led to infection] we know this is extremely contagious and some people are spreading it more than others," Berejiklian said.
"And what we want to avoid at this stage is a superspreader event. With this current outbreak, we have not experienced a superspreader event. That is what we want to prevent."
Chief health officer Dr Kerry Chant said at the moment everything appeared to be linked and can be explained, but stressed the importance of high testing rates.
She called on Sydneysiders to "stress our labs to the ultimate of their testing capacity", saying "the quicker we can diagnose cases, the quicker we can get ahead of the transmission of this virus".
The highly contagious nature of the Delta variant has put authorities on high alert, with the virus appearing to pass through fleeting contact.
CCTV footage showed a man in his 50s caught the virus after merely passing through the "airspace" of the limousine driver, who is at the centre of the latest outbreak, in Myer at Westfield Bondi Junction.
"The gentleman in his 50s, was no more than seconds in the near vicinity of the limousine driver," Health Minister Brad Hazzard said over the weekend.
"It would appear he was somewhere in the range of between 10 and, possibly, 50-60 centimetres away in a passing situation.
"Each of them had stood not far away from each other for a very short period of time and then it would appear that one of them possibly moved through the airspace that the other one had occupied."
Hazzard called on anyone who visited Westfield Bondi Junction during the times stated on NSW Health's website to get tested even if they were not in one of the specific stores or sites mentioned.