Australia's New South Wales state has reported its biggest daily rise in locally acquired coronavirus infections this year, with authorities warning that worse may yet to come for Sydney, which is in a three-week hard lockdown.

There were 50 new cases of community transmission in the country's most populous state, up from 44 a day earlier, the previous 2021 record high. This brings the outbreak of the highly infectious Delta variant to 489 cases, according to a Reuters report.

“When you know that there are 26 cases infectious in the community, the only conclusion we can draw is that things are going to get worse before they get better,” state Premier Gladys Berejiklian told a televised briefing.

“I think it is pretty clear that unless we reduce that level of people in the community that are infectious, we won't be able to turn things around as quickly as we can or as quickly as we should.”