Sydney, Dec 21 (IANS): Australia's domestic borders on Monday slammed shut to residents of Sydney, as a newly-discovered coronavirus cluster in the country's biggest city has increased to 83 after 15 more people tested positive.

Concerns over how far the cluster has spread prompted differing responses by state leaders across the country, reports Xinhua news agency.

Western Australia has re-implemented a hard border closure for the entire New South Wales (NSW), of which Sydney is the capital, turning back anyone from the latter state without a legitimate exemption.

Victoria and Queensland have closed their borders just to the Greater Sydney region, allowing residents of the two states until the end of Monday to get back across the border before restrictions apply.

Meanwhile, South Australia and Tasmania introduced softer restrictions requiring arrivals from the Greater Sydney region to quarantine for 14 days.

The area where the outbreak originated, Sydney's Northern Beaches, will remain in lockdown until Wednesday.

Residents from the Greater Sydney area were asked to limit their movements.

Conditions on residents in the Northern Beaches were similar to those during NSW's initial Covid-19 outbreak earlier in March, allowing them to leave their homes only to work, shop for necessary items, provide care or take brief isolated exercise.

On Sunday, NSW recorded its highest number of tests conducted in a single day, with 38,578 people tested.

The state's Premier Gladys Berejiklian told reporters that a tightening of restrictions over Christmas would take place if warranted by the numbers of new cases over the coming week.

The state of NSW currently accounts for 4,771 coronavirus cases and 53 deaths.

Australia has so far reported a total 28,171 cases and 908 fatalities.