Australia's New South Wales (NSW) state authorities said they were still finding a significant number of new Covid-19 cases in the community, raising worries of fresh clusters as it reported a rise in new infections for the third day in a row.

Half of Thursday's total 24 cases were detected in the community, while the others infected were already in home quarantine, officials said, as Sydney nears a week of a hard lockdown put in place to contain an outbreak of the highly infectious Delta variant.

“(This) is a cause of concern. That is what we will be looking at in the next few days and beyond as a measure of our success,” NSW state Premier Gladys Berejiklian told reporters in Sydney.