Sydneysiders were largely banned from leaving the city as Australian authorities rushed to stop a growing outbreak of the highly contagious Delta Covid-19 variant from spreading to other regions.

More than 30 people have been diagnosed with Covid-19 since the cluster emerged in the city's Bondi Beach area last week, the latest in a string of flare-ups that highlight Australia's difficulty in extinguishing outbreaks, AFP reports.

New South Wales state Premier Gladys Berejiklian announced new restrictions that will apply for the next week, including the immediate ban on non-essential travel out of Sydney and limits on social gatherings.

A “very huge proportion” of Sydney's five million residents are subject to the travel ban, which applies to seven local government areas where Covid-19 cases have been detected, she said.