SYDNEY, Aug 4 ― Australia's Queensland state reported 16 locally acquired Covid-19 cases today as authorities warned a lockdown in state capital Brisbane might be extended beyond Sunday if people flout the tough restrictions.

It was the same number of cases as detected yesterday, and seven were linked to three schools.

Infections from the highly infectious Delta variant have plunged southeast Queensland, which includes Brisbane and some neighbouring regions, into a lockdown as officials rush to douse the outbreak, the biggest in more than a year.

State Deputy Premier Steven Miles implored residents to avoid all non-essential shopping and remain home.

"Every time someone leaves their home they increase the risk that this lockdown may need to go on longer ... now is not the time to buy outdoor furniture, there will be time before summer to get sun lounges,” Miles told reporters in Brisbane.

Officials fear the virus may have spread to Cairns, some 1,700 kilometres (1,056 miles) north of Brisbane after a vaccinated ship pilot tested positive for the Delta strain.

Sydney, the country's largest city, is also in lockdown until August 28 as daily cases have spiked to record levels.

Snap lockdowns, speedy contact tracing and strict social distancing rules have helped Australia tame prior outbreaks and keep its Covid-19 numbers low, with just over 34,800 cases and 925 deaths since the pandemic began.

But the fast-moving Delta strain has alarmed authorities while a slow vaccine rollout frustrated residents. Only about 20 per cent of people older than 16 have been fully vaccinated. ― Reuters