NSW Premier Gladys Berejiklian also announced the state was extending some of the restrictions because it was "important for all of us to be on high alert," she said.
Masks on Sydney public transport, which were made mandatory on Friday, will now be extended to Shellharbour and Wollongong until Thursday.
And people in seven local government areas - Randwick, Bayside, Botany Bay, Inner West, City of Sydney, Waverley and Woollahra - will now also have to wear masks indoors unless they are eating or drinking.
NSW Health is conducting urgent investigations and is asking those who visited Westfield Bondi Junction, including the car park, to get a Covid-19 test, even if they do not have any symptoms.
The latest venues of concern can be found here.
NSW Health Minister Brad Hazzard said the highly contagious Delta variant was posing a real threat to Sydney residents.
Hazzard said CCTV footage of how one person contracted the virus had highlighted the highly contagious nature of the latest strain of Covid-19.