A cruise ship operator has reassured the public that all passengers are in "good health" after false reports that a Norwegian Jewel ship had been placed in lockdown in Sydney Harbour due to a possible coronavirus case.

The cruise ship arrived in Sydney from Auckland on Friday morning, docking at the international passenger terminal at Circular Quay.

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"This morning, there were various false media reports related to an illness on board our ship. There is absolutely no truth to this," a spokesperson for Norwegian Cruise Line, which operates the Norwegian Jewel ships, told SBS News.

"We have no guests with any respiratory-related illness on board. The vessel remains in operation and all guests on board are in good health."

While some passengers said they were delayed from disembarking for approximately 45 minutes, a spokesperson for the Port Authority of New South Wales told SBS News this was due to new screening procedures implemented by NSW Health, and not a suspected case of coronavirus.

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"Before anyone can disembark the ship, they are going on board, screening those passengers and if all clear, everyone will come off the ship," the spokesperson said. "So, that is causing a delay but the ship isn't in lockdown or anything like that."

All passengers have now disembarked the ship.

The spokesperson said that reports of a passenger being taken to hospital overnight was unrelated to the coronavirus, which is now known as COVID-19.

An NSW Health spokesperson confirmed that all passengers had been screened for the coronavirus before disembarking and that there was "no outbreak of any disease on board".

Three passengers had been transferred for medical care unrelated to respiratory illness, the spokesperson said, and one person was tested for respiratory illness on board the ship.

"Testing was done as a precaution as there is no indication that the person is at particular risk of COVID-19, and at this point, there is no concern for other passengers or people in and around Circular Quay," they said.

None of the people on board had been to China within the past two weeks.

The precautionary testing comes as the number of coronaviruses cases linked to the quarantined Diamond Princess cruise in Japan jumped to 218, including 12 Australians.

The ship is scheduled to depart Sydney on Friday for a 14-day cruise around Australia and New Zealand, a company spokesperson said.