More than a dozen new cases of coronavirus in New South Wales have been linked to a cruise ship that was docked in Sydney Harbour.

The Ruby Princess returned to Sydney on Thursday after visiting New Zealand.

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There were 1,148 crew and 2,647 passengers on board - the latter of which were allowed to disembark and potentially spread the infection through the city.

Doctors initially tested 13 unwell patients for COVID-19. Three passengers and a crew member were found to have the virus.

However, that number has now risen to 18 people.

NSW Premier Gladys Berejiklian. Credit: DEAN LEWINS / AAPIMAGE

All confirmed cases are in self-isolation either at home or in hospital, according to NSW Health.

All passengers and crew have been notified and are being advised to self-isolate for 14 days and monitor symptoms.

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The surge in cases related to the ship comes as a further 97 cases are reported in NSW.

There are now 533 cases across the state and more than 1,100 nationwide.

NSW Premier Gladys Berejiklian says the state is now preparing a “comprehensive shutdown” of “non-essential” services.