'Some signs' Vic virus numbers stabilising

There are some signs the number of coronavirus cases in Victoria is stabilising but authorities say it's too early to know for certain.

There were 66 new cases of coronavirus in Australia on Friday, all from Victoria.

It marks the 17th day of double-digit increases in the state, but the numbers are slightly better than the 77 new cases on Thursday.

Deputy Chief Medical Officer Michael Kidd says the number hasn't been rising substantially day-to-day despite the high volume of tests being conducted.

"This is a strong indication of the effectiveness of the measures which are being implemented in Victoria," he told reporters in Canberra on Friday.

"The figures are showing some signs of stabilisation but it is too early to confirm."

Dozens of suburbs across Melbourne entered the second day of a reinstated lockdown on Friday, with the Victorian government announcing almost $2 million extra for mental health support for people in the hot spot areas.

"If you find yourself back in isolation and you are feeling fearful or distressed or despondent, please reach out for assistance and support," Professor Kidd said.

The Morrison government is concerned Melbourne's coronavirus outbreak could threaten Australia's economic recovery.

Senior cabinet minister Simon Birmingham vowed to put partisan politics aside to work with the Victorian Labor government on squashing the disease.

"We have a situation in Victoria that is threatening the economic recovery that is so important for all of us," he told Sky News.

Prime Minister Scott Morrison spoke with world leaders in other countries performing well in Europe, the Americas and Israel on Thursday night.

He says the situation in Victoria is consistent with what's occurring in other countries that are reopening their economies.

"We're on top of it, we're getting on top of it more broadly," Mr Morrison told Sounds of the Mountains radio.

"Yes, it's very concerning, but it is important that we understand the context and so the COVID-19 impact will be there on our economy for some time to come."

Victoria's government is under pressure after serious breaches were alleged in hotel quarantine and a coronavirus-infected man left his two-week stint without being tested.

NSW recorded no new cases on Friday after eight on Thursday, including a supermarket worker who tested positive after spending two weeks in Melbourne hotel quarantine.

Visitors to the ACT from Melbourne hot spots will be forced to self-isolate for 14 days or return home immediately.

South Australia is maintaining its border restrictions with NSW, the ACT and Victoria, as health authorities closely monitor the situation in Melbourne.