"We're sorry; that's not something we want to do, but we must do for our own safety," he said.

"As soon as you set foot in NSW you'll be exposed to the possibility of six months' jail or an $11,000 fine."

Victorian Premier Daniel Andrews said there will be new testing locations across all the hotspot postcodes that are re-entering lockdown from midnight. “There is such a big team of people working as hard as they can … to have control of this virus,” he said.

Speaking to reporters on Wednesday morning, Mr Andrews asked families in those areas to work with the health officials and the government.

"I don’t want to have to shut down any more postcodes," he said.

Mr Hazzard warned anyone from NSW who travels to the Victorian hotspots would be liable for the same penalties.

"If you choose to go there when you really shouldn't be going there, and you come back to NSW, you'll be required to go into isolation here for 14 days," Mr Hazzard said.

"And if you breach that order, you'll be liable to a penalty ... it could be an $11,000 fine or a six-month jail sentence."

Mr Hazzard said the NSW Health order banning Victorian hotspot travellers was 90 per cent complete, and he would sign the order later on Wednesday.

"I expect that our orders will become operative from midnight tonight," he said.

'You're very mortal'

Mr Hazzard stressed that people in NSW – and particularly younger people – should continue to take the pandemic seriously.

"I am concerned that young people particularly think that they are invincible and immortal," he said.

"Well, no. You're very mortal, and we have had people as young as 17 across the world who have passed away ... so you need to take it seriously."

The Health Minister's warning comes with the news that one of the 63 COVID-19 patients being treated by NSW Health has been moved to intensive care. That patient does not require a ventilator.

More than 16,000 tests were conducted in the 24 hours to 8pm on Tuesday, up from 12,250 in the previous reporting period.

With Mary Ward