Carnival Australia's Majestic Princess cruise ship was docked in Sydney, the capital of the most populous state, New South Wales, with "in the vicinity" of 800 passengers on board testing positive to the virus, the company said.
The state health authorities rated the outbreak's risk level at "Tier 3", indicating a high level of transmission.
The incident has sparked comparisons with a notorious 2020 outbreak onboard the Ruby Princess cruise ship. That outbreak, also in New South Wales, led to 914 infections and 28 deaths, an inquiry found.
Home Affairs Minister Clare O'Neil said the authorities have created "regular protocols" in the wake of the Ruby Princess episode and that New South Wales Health would take the lead on determining how to get passengers off the Majestic Princess "on a case by case basis".
Federal border force officer will play a supplementary role to the state authorities, O'Neil told reporters in Melbourne.
Carnival Australia, part of global leisure company Carnival Corporation & plc, said COVID-positive passengers were isolating onboard and being cared for by medical staff, according to New South Wales Health. The agency said it was working with cruise ship staff to monitor the health of passengers and crew members.
Company president Marguerite Fitzgerald told ABC television that once Carnival saw an elevated number of COVID cases, it put extra protocols in place.
The outbreak comes as COVID-19 cases rise across Australia, reflecting community transmission of the Omicron variant XBB, the federal government said this week.
(With inputs from Reuters)
