Australia's New South Wales state authorities on Wednesday extended a COVID-19 lockdown in state capital Sydney for another month after weeks-long curbs failed to contain an outbreak of the highly infectious Delta virus variant.

Lockdown rules were due to end on Friday but restrictions will now run until August 28, state Premier Gladys Berejiklian told reporters in Sydney.

A total of 177 new locally acquired cases were detected in New South Wales, up from 172 a day earlier.