Watch live: Victorian Health Minister provides COVID-19 update after NSW urges 'measured' response

Victoria has declared anyone travelling to Victoria from this "red zone" must quarantine for 14 days in government-run hotel accommodation at a cost of $3000. People from other parts of the state, including regional areas, must get permits to move freely cross the border.

While Ms Berejiklian said it was the right call to declare the city's northern beaches a hot spot, she said the majority of NSW was still unaffected.

"The advice I have received to date suggests we will get at least the same number of cases if not more tomorrow at this time, so it is a hot spot," she said.

"But I ask state leaders to be measured in their response because to date there is no evidence that it is outside the northern beaches, although we are concerned and we are keeping a close eye on it to make sure that is definitely the case."

She has not moved to lock down Greater Sydney but has asked residents to cancel plans and stay home, and flagged possible restrictions from Sunday depending on numbers and health advice.

Acting Chief Medical Officer Paul Kelly also said he hoped other states and territories would take a measured approach to travel restrictions for Sydneysiders over Christmas.

"For the first time, the northern beaches of Sydney were declared a hot spot yesterday in anticipation for the extra cases that have occurred overnight," Professor Kelly said. "I very much welcome the other states that are using that type of approach, so limiting it to where the problem is.

"I would hope they will make that a proportionate thing as we have a lead-up to Christmas," he said, adding border restrictions were a matter for state and territory governments to decide themselves.

Ms Berejiklian also called on other states to "lift their game" in taking more repatriated travellers into their respective quarantine systems.

"I don't think we should discriminate who flies in where ... but what I do request is that the other states lift their game [and] only take on more, I know Victoria has," she said.

"We don't mind doing our bit in New South Wales but we want the other states do their bit as well and that remains the case."

The Victorian government has declared the northern beaches area a "red zone" and visitors from there who enter Victoria will have to undergo a 14-day, $3000 hotel quarantine stay.

Travellers flying from New South Wales into Victoria now need to have a permit to enter.

At Melbourne Airport on Saturday morning, rows of authorised officers and nurses, gowned-up and wearing full personal protective equipment, asked to see permits from people arriving from Sydney.

A touted testing station for Qantas travellers was not yet operational according to passengers. A pop-up station for Jetstar passengers was operational early on Saturday.

Victoria has not shut the border to NSW but Victorian Chief Health Officer Brett Suttonstrongly advised Victorians not to travel to Sydney for the foreseeable future. He expected the edict would likely stay in place for at least two weeks to assess the virus’ true spread through the city.

His comments were echoed by Health Minister Martin Foley: "If you’re travelling to Sydney and you don’t have to, please don’t".

"If you are coming from Sydney and you don’t have to come please don’t come. Come when this is over," he told reporters on Friday.

Professor Sutton said he was concerned by the steep hike in cases since the first person was diagnosed on Thursday.

"We can and should expect additional cases to occur," he said.

A United Airlines crew member who arrived in Sydney with COVID-like symptoms on Monday was released from hotel quarantine within 24 hours despite a request from health authorities for more time to perform further testing.

The female crew member landed in Sydney from Los Angeles with symptoms and subsequently tested negative to COVID-19.

But a government source with knowledge of the events said the woman was released to fly home to the US after lobbying by an airline executive, despite NSW Health quarantine teams wanting to retain her for a second test.