It is the highest caseload recorded in NSW since October 9, two days before lockdown lifted, and the second day in a row with more than 500 cases.

The three additional Omicron cases take the total in the state to 45, with health authorities expecting genomic testing to soon identify more.

Health authorities are concerned festive season celebrations are driving the spike in cases, and are urging caution.

"Clearly we have seen a number of outbreaks recently across Sydney," NSW Health's Dr John Hall said on Saturday.

"That is why it's so important, as the festive season and Christmas approaches, that everyone remains vigilant when gathering to celebrate with friends, family and colleagues.

"We reiterate just how important it is for people to not attend social functions if they have any symptoms, even if mild."

NSW Health is already battling to contain several large transmission events.

A trivia night at a Sydney pub sparked a new cluster of cases, with at least 46 patrons testing positive to the virus after attending the Oxford Tavern in Petersham on November 30.

Authorities are also concerned about 140 passengers who embarked on a Sydney Harbour cruise on Friday night which has so far resulted in at least five cases of the Omicron variant.

Authorities now also believe an Omicron case attended the Albion Hotel in Parramatta and Cult Nightclub in Potts Point.

Alerts have also been issued for the Golden Sheaf Hotel in Double Bay, Woody's Surf Shack Night Club in Byron Bay - which has also been linked to at least three cases - and an event at the Coorabell Hall on Saturday night, which has resulted in 16 cases so far.

There are 150 COVID-19 cases in hospital, with 25 people in intensive care, eight of whom require ventilation.

A man in his 80s who was a resident of the Gillawarna Village Aged Care facility in Sydney, where he acquired his infection, was among the deaths announced on Saturday.

He had received three doses of a COVID-19 vaccine but had underlying health conditions.

It is the second death linked to the facility.

Two other fully vaccinated people - a woman in her 70s and a man in his 80s - also died on Friday.

The double dose vaccination rate of those aged over 16 in NSW hovers around 93 per cent, while 77.6 per cent of children aged between 12 and 15 have had two doses.

Australian Associated Press