There are now five Omicron cases connected to a cluster at an indoor climbing gym and two Western Sydney schools, NSW Health says.
There are now 15 cases of Covid-19 with the Omicron variant across the state.
A confirmed case in the ACT has also been linked to the Sydney Indoor Climbing Gym at Villawood.
All year three and year four students and teachers at St Peter Chanel Catholic Primary School at Regents Park have been deemed close contacts and asked to self-isolate following a student from the school confirmed as s new case of Omicron.
Anyone who attended the Sydney Indoor Climbing Gym on Saturday November 27 between 9am and 4.30pm is a close contact who must immediately get tested and isolate. People should continue to monitor for symptoms and if any symptoms occur, get tested.
This follows an outbreak of cases connected to Regents Park Christian School.
NSW Health said genomic sequencing is underway on a number of other cases linked to the schools and gym.
Promisingly, there have been no cases with the Omicron variant admitted to hospital in NSW for treatment of Covid-19, however the effect of the variant on the rate of hospitalisations is not yet known so early in its emergence.
NSW recorded another 286 new cases of coronavirus on Sunday from 66,671 tests.
On Sunday there were 148 people in hospital, up nine from the day before, with 26 in intensive care and five on ventilators.
The state's vaccination rate remained at 94.6 per cent first-dose coverage on Saturday with 92.8 per cent fully vaccinated.
Children to receive at least one dose before 2022 school year
Federal Health Minister Greg Hunt announced on Sunday the Therapeutic Goods Administration (TGA) has provisionally approved the Pfizer vaccine for children aged between five and 11.
It comes as fears grow over the Omicron coronavirus variant with concern the variant is spreading in the NSW community.
"The vaccine dose approved by the TGA for children aged five to 11 is the same safe and effective vaccine used for other age cohorts, however is one-third the dose approved for those aged 12 and over."
"It is about keeping our kids safe, keeping our families safe, keeping all Australians safe," Mr Hunt told reporters on Sunday.
"In terms of the vaccination program, that continues to go from strength to strength."
Do you have a story tip? Email: firstname.lastname@example.org.