Australia's Victoria state reported fewer new local Covid-19 cases, the first day of a one-week hard lockdown imposed to contain a highly infectious outbreak which authorities said could become uncontrollable.

Four new locally acquired cases were reported in the last 24 hours, down from 12 a day earlier, taking the total infections in the latest cluster to 30 but officials urged people to remain cautious and follow lockdown rules.

“We are very, very early in this [...] community transmission is still expected to occur,” Victoria state Chief Health Officer Brett Sutton told reporters in the state capital Melbourne.