Victoria has detected 288 new infections in the past 24 hours - the highest daily tally for an Australian state since the pandemic began.

New South Wales had previously seen the greatest number with 211 in March, when travellers returning from overseas were Australia's biggest concern.

The current outbreak, centred in Melbourne, has worsened dramatically due to local transmissions in the past three weeks.

"I know and understand there will be concern across the community to see that number," Premier Daniel Andrews has just told Victorians.

"It was always going to get worse before it got better. We are doing more testing than has ever been done - not by a small margin - but by a massive margin."

More than 37,000 tests were carried out yesterday, he added.

Melbourne's five million residents were ordered back into lockdown yesterday amid fears the city's outbreak could spread elsewhere. Other states have seen relatively few recent infections.

Australia has recorded about 9,000 cases and 106 deaths.