Australia is seeing a new surge in coronavirus cases.

The chief health officer for Victoria state, where the city of Melbourne is located, announced 270 new cases on Tuesday, following an increase of 177 on Monday.

Brett Sutton said 28 of the new cases had been linked to a known outbreak but that the rest were still being investigated.

Last week, Melbourne reimposed strict public health emergency measures, establishing a "hard boundary" around the city and the closing of its borders with New South Wales in an effort to stop the spread of the virus.

"We have over 1,800 active cases in Victoria," Sutton said. "That's a really significant number of people with coronavirus, and it does mean that in the next fortnight we're going to see a number of people who will require hospital."

He said the state's surge in cases will result in at least 200 people requiring hospital care within the next two weeks.

"There's often 10% to 20% of all coronavirus infections who require hospitalization, so that's a couple of hundred individuals at least," Sutton said, according to The Age newspaper.

Sutton said Melbourne and its northern suburb of Mitchell Shire could be brought to stage 4 restrictions — higher than for the rest of Victoria, if the numbers didn't come down.

"I hope to see that this week, but there are no guarantees," he said.

Meanwhile, the state of South Australia has decided to delay lifting border restrictions imposed on the capital, Canberra and New South Wales, where a rise in coronavirus cases in Sydney has caused concern.

Australia's cases peaked in late March, but had fallen dramatically in the weeks thereafter. However, they have started to rise again since late last month. More than 10,000 Australians have tested positive for the coronavirus since the start of the pandemic, with 108 deaths.

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