SYDNEY (REUTERS) - Australia's most populous city recorded its deadliest day from the Covid-19 pandemic on Monday (Aug 16), while residents in Melbourne face a nightly curfew and a further two weeks of lockdown amid a surge in infections.

Sydney, which is in its eighth week of lockdown, is the epicentre of Australia's third Covid-19 wave that threatens to push the country's A$2 trillion (S$1.99 trillion) economy into its second recession in as many years.

New South Wales state Premier Gladys Berejiklian said seven people had died from Covid-19 in the past 24 hours, surpassing the state's previous daily record from earlier this month.

Ms Berejiklian said New South Wales has also detected 478 infections, the highest one-day rise since the pandemic begun.

"Our community transmission numbers are disturbingly high," Ms Berejiklian told reporters in Sydney. "Every death is a person who has loved ones, who has died in tragic circumstances, and our heartfelt condolences to all of those loved ones and families."

The authorities also confirmed the death of a 15-year-old boy from Sydney, who had pneumococcal meningitis and Covid-19.

Australia has confirmed 55 deaths since July 11, breaking a run of more than three months without any fatalities. In total, Australia has recorded 966 Covid-19 deaths.

The toll rose as 200 military personnel were deployed across Sydney to set up roadblocks in the hardest-hit areas, amid persistent reports of people flouting lockdown rules. The latest deployment comes on top of 500 troops deployed last month.

Lockdowns

With only 26 per cent of people above 16 years of age fully vaccinated, Australia is vulnerable to the highly infectious Delta variant that has steadily spread across the country.

While Sydney, Melbourne, Canberra and Darwin - which begun its curbs on Monday - are all in lockdown, cases have proved stubbornly difficult to suppress.

Victoria state Premier Daniel Andrews said Melbourne will now remain in lockdown until Sept 2, after recording 22 new Covid-19 cases. Melbourne's five million residents will also be subjected to a nightly curfew.

"We are at a tipping point. There is simply no option today but to further strengthen this lockdown," Mr Andrews told reporters in Melbourne.

A spike in cases had been driven by people breaking lockdown rules, he said. In one instance, police fined 69 people A$5,500 (S$5,472) each for attending an engagement party in breach of the lockdown.

Canberra, the national capital, recorded 19 new cases, the biggest one-day rise in cases on Monday as it extended its lockdown for a further two weeks.

Australia's economy rebounded strongly from the initial wave of the pandemic, with unemployment hitting its lowest levels in more than a decade at 4.9 per cent in June. But with many of its most populated cities on the east coast now in lockdown, economists expect a heavy toll.

"Unemployment may spike back up to 5.5 per cent in the months ahead, mainly driven by (New South Wales)," said Mr Shane Oliver, chief economist at AMP.

Vaccines

The outbreak and sluggish vaccine roll-out has fuelled pressure on Prime Minister Scott Morrison, who must return to the polls before May next year.

A poll last week showed his approval rating at its lowest level since the pandemic began.

Australia had bought about one million doses of Pfizer's Covid-19 vaccine from Poland with more than half rushed to inoculate the 20- to 39-year-olds in the worst-affected suburbs of Sydney.

Mr Morrison declined to specify how much Australia had paid for the vaccines, which will be in addition to 40 million dose his government has ordered from Pfizer.