Residents of Greater Sydney, including the Central Coast and Blue Mountains, will be banned from travelling to Victoria from midnight on Sunday with Premier Daniel Andrews declaring the entire region a red zone.
Anyone who enters the state after that time will be subjected to 14 days of hotel quarantine.
Returning Victorians have an additional 24 hours to make the trip home, where they will be expected to self-isolate for 14 days at home.
Those arriving after midnight on Monday will also be subjected to hotel quarantine arrangements.
Mr Andrews said the significant new step was a “difficult decision, but it is the appropriate decision”.
He said the border closures would remain in place for “as long as they needed to” and would not be lifted when the current Northern Beaches lockdown expires at midnight on Wednesday.
Victoria has gone 51 days without a locally-acquired case of COVID-19.
An additional 30 cases were recorded in NSW in the 24 hours to 8pm on Saturday, taking the Northern Beaches outbreak to 70.
The majority of the new cases – 28 – were linked to the Avalon cluster, with the two remaining cases, both in Northern Beaches residents, yet to be identified.
Authorities have conducted 28,000 tests in the past 24 hours.
NSW Premier Gladys Berejiklian has warned current restrictions could be extended beyond Wednesday as the number of new cases continues to rise.
People in Australia must stay at least 1.5 metres away from others. Check your jurisdiction’s restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
News and information is available in 63 languages at sbs.com.au/coronavirus. Please check the relevant guidelines for your state or territory: NSW, Victoria, Queensland, Western Australia, South Australia, Northern Territory, ACT, Tasmania.