Australia's second most populous city began a six-week lockdown on Thursday following a spike in new coronavirus cases, as states around the country tightened internal borders to prevent a second wave sweeping the country.

Australia has avoided the high casualty numbers of other countries to the COVID-19 pandemic, which has killed 544,055​ people globally, but an outbreak in Melbourne prompted the state of Victoria to impose "self isolate" orders for the city's estimated five million.

Victoria on Wednesday reported 134 new infections, down on the previous day's record increase but well above the rate of other states.

Other states and territories have recorded few or zero cases in recent weeks and are continuing to reopen their economies.

The northern state of Queensland said it would ban non-residents arriving from Victoria. It will open its borders to people from other states and territories on Friday.

Even people travelling from Victoria who were willing to pay for the mandatory 14-day hotel quarantine would be banned, the Queensland government said.

"They are making the decision that that two weeks and that cost is worth it to get out of Victoria," deputy premier Stephen Miles said in a televised news conference.

"We don't want that to continue," he added.

The country's most populous state, New South Wales (NSW), closed its heavily trafficked border to neighbouring Victoria on Wednesday. South Australia also closed its border with Victoria.

"We're definitely at a different stage of the pandemic," NSW Premier Gladys Berejiklian told reporters in Sydney.

The NSW authorities reported 13 new coronavirus cases in the 24 hours to Thursday morning, of which 11 were overseas arrivals in hotel quarantine and two were members of a family who had returned from Melbourne. NSW says anyone arriving from Victoria must self-isolate for 14 days.

The island state of Tasmania kept its border closed to Victoria and extended a state of emergency to the end of August because of the Victorian outbreak. Tasmania itself has not reported a new case in nearly eight weeks.

Western Australia state had closed its border to the rest of Australia indefinitely before the latest outbreak in Victoria.

After enforcing restrictions early in the coronavirus outbreak compared to most other countries, Australia had begun to ease its lockdown in May to revive its economy after a significant slowdown in infection rates.

Australia has so far recorded about 8,900 infections and 106 deaths by Thursday.