Army patrols Sydney streets as Brisbane extends COVID-19 lockdown

Sydney, Australia's largest city, is into its sixth week of a lockdown as it struggles with a spike in infections that added nearly 3,500 cases since the first one was detected in a limousine driver who transported overseas airline crew.

Officials in New South Wales, of which Sydney is the capital, have implored residents to stay home to prevent more surges and brought in the military to help police enforce compliance after some defied lockdown rules.

Some 300 army personnel, who will be unarmed and under police command, will go door to door to ensure people who have tested positive are isolating at their homes.

After a steady rise in new cases, the lockdown rules in southeast Queensland, which includes Brisbane, will run until Sunday as officials fear there could be more undetected cases in the community and urged residents to get tested. Restrictions were due to end Tuesday evening.

Thirteen locally acquired cases were detected in Queensland state, up from nine a day earlier.

Australia is going through a cycle of stop-and-start lockdowns in several cities after the emergence of the fast-moving Delta strain and such restrictions are likely to persist until the country hits a higher vaccination coverage.

Prime Minister Scott Morrison has promised lockdowns would be "less likely" once the country inoculates 70% of its population above 16 years, which now stands at 19%. Morrison expects to hit that mark by the end of the year.