Prime Minister Scott Morrison speaks with the media. File photo

Australia will likely slow down the return of its citizens from abroad, Prime Minister Scott Morrison said on Wednesday, as it grapples with a fresh outbreak of the coronavirus that has led it to isolate its second most populous state.

The border between Victoria and New South Wales, the busiest in the country, was closed overnight and around 4.9 million residents in the Victorian capital of Melbourne will return to partial lockdown at midnight following a spike in COVID-19 cases in the city.

A woman wearing a face mask, amid concerns of the COVID-19 coranavirus, walks on a street in Sydney. File/AFP

"The rest of the country knows that the sacrifice that you're going through right now is not just for you and your own family, but it's for the broader Australian community," Morrison said during a televised media conference.

"I can imagine the frustration ... we don't have control over the virus as such, but we do have control over how we respond."

With the Victoria shutdown putting pressure on other states, Morrison said he would take a proposal on Friday to the national cabinet created to deal with the pandemic, seeking to slow down the return of Australian citizens and permanent residents by reducing the number of repatriation flights. The two groups have been the only arrivals allowed since Australia closed its international border in March.

Neighbouring New Zealand has already taken that step, announcing on Tuesday that its national airline will not take new inbound bookings for three weeks to reduce the burden on overflowing quarantine facilities.

There has been growing public concern in Australia about security lapses that have led to returnees spreading the virus, despite undertaking quarantine on arrival. Victoria has begun an inquiry into how the state went from the brink of eradicating the virus to soaring infection numbers.

The state reported 134 new infections in the 24 hours to Wednesday morning, down from the previous day's record 191 but well over the low single digit daily increases of the other states and territories.

Of the new cases, 75 were occupants of nine public housing towers that were earlier this week placed under the country's strictest lockdown so far. Around 3,000 residents have been banned from leaving the buildings, which are under police guard, for five days. All residents are being tested for COVID-19.