Masks will be mandatory on public transport in the Wollongong and Shellharbour council areas from 4pm on Sunday, with nine COVID-19 cases now linked to the Bondi cluster.
This follows NSW Health announcing two Illawarra businesses as COVID-19 exposure sites.
NSW recorded two locally acquired cases of COVID-19 in the 24 hours to 8pm on Saturday, one of which was announced Saturday morning.
NSW Health has also been notified of two new locally acquired cases overnight. These cases will be included in Monday's numbers.
Three new overseas-acquired cases were recorded in the same period, bringing the total number of cases in NSW since the beginning of the pandemic to 5453.
Masks are mandatory on public transport in Greater Sydney and the Blue Mountains, and this is now being extended to include the Wollongong and Shellharbour council areas from 4pm on Sunday.
Several of the recent new cases have been detected in those areas.
"Even though they are directly linked to the Eastern Suburbs cases, we are concerned there may have been spread in the community," Premier Gladys Berejiklian said on Sunday.
"It is important for all of us to be on high alert, no matter where we live."
The Illawarra Shoalhaven Local Health District has also "strongly encouraged" all people in the Shellharbour and Wollongong local government areas to wear masks at indoor venues, under new NSW Health advice.
The ISLHD is also requiring people entering their health facilities to wear a mask and to maintain good hand hygiene as well as to practise social distancing wherever possible.
There are now nine cases linked to the Bondi cluster. Of the locally acquired cases to 8pm on Saturday:
*One was announced on Saturday. He is a man in his 30s who lives in Sydney. He attended Westfield Bondi Junction and spent time in the Wollongong area.
*The second case is a household contact of the man in his 30s who also attended Westfield Bondi Junction and spent time in the Wollongong area.
Of the two new locally acquired cases notified overnight:
*One is a woman in her 50s from the Sutherland Shire. She is a close contact of a previously reported case and has been in isolation. This case will be included in Monday's numbers.
*One new case is a man in his 50's from the Sutherland Shire. He is a close contact of a previously reported case and has been in isolation. This case will be included in Monday's numbers.
While acknowledging that "all of us are a bit fatigued after so many months of living with COVID", Ms Berejiklian urged NSW residents to remain vigilant in following restrictions and in coming forward for testing.
"We have to make sure we aren't complacent and make sure we are complying to what we are asking you to do," she said.
"Please, we don't want to extend further restrictions unless we must."
ISLHD acting chief executive Caroline Langston thanked the Illawarra community for coming forward for testing despite the wintry weather and said several clinics in the area, many of which are drive-throughs, had extended their hours in response to the latest cases.
"High rates of testing help us to detect any cases in the community as early as possible so I again encourage people to remain vigilant for COVID-19 symptoms and to get tested for even the mildest of symptoms," Ms Langston said.
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In addition, masks will become mandatory in all public indoor venues in the City of Sydney, Waverley, Randwick, Canada Bay, Inner West, Bayside, and Woollahra local government areas.
These venues include retail, theatres, aged care facilities and for front-of-house hospitality staff.
There were 24,468 tests reported to 8pm on Saturday, compared with the previous day's total of 26,631.
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