A holiday cruise ship carrying about 800 passengers with Covid-19 has docked in Sydney, Australia.

The Majestic Princess cruise ship arrived at Circular Quay, having sailed from New Zealand.

About 4,600 passengers and crew were aboard the ship when it docked - meaning around one in five had Covid.

The outbreak is reminiscent of the Ruby Princess cruise ship Covid outbreak of early 2020, where at least 900 people tested positive and 28 died.

Marguerite Fitzgerald, the president of cruise operator Carnival Australia, said a large number of cases started to be detected about halfway through the 12-day voyage.

All cases were either asymptomatic or mildly symptomatic, she said.

Staff would be assisting all guests who have tested positive "with accessing private transport and accommodation to complete their isolation period", she said. The ship will soon depart for Melbourne.

Asked about comparisons between the Majestic Princess and the Ruby Princess - which also belongs to the same operator - Ms Fitzgerald said: "Since then, we as a community have learnt a lot, a lot more about Covid."

The outbreak comes as Covid cases rise across Australia.

In New South Wales, 19,800 new cases were detected in the seven days to Friday.