Residents visit a pharmacy in the Fairfield suburb of Sydney on Monday during the city's prolonged COVID-19 coronavirus lockdown. Photo: AFP

Australia's most populous city recorded its deadliest day of the COVID-19 pandemic on Monday, as hundreds of unarmed military personnel were deployed across Sydney in a desperate attempt to quell a "disturbing high" number of infections.

Sydney, which is in its eighth week of lockdown, is the epicenter of third Australia's COVID-19 wave that threatens to push the country's A$2 trillion ($1.5 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 record day from earlier in August.

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," 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 toll was announced as 200 military personnel were deployed across Sydney to set up roadblocks to enforce restrictions of movement. Australia in July deployed 500 troops to help New South Wales.

With only 26 percent 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 are all in lockdown, cases have proved stubbornly difficult to suppress.

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.

Reuters