NSW will send people who have been overseas in the two weeks before their arrival into three days of home quarantine, as the state works out its response to the threat posed by a new, "concerning" variant of COVID-19.
Premier Dominic Perrottet says precautionary steps are needed to protect against the Omicron variant while experts investigate the risk.
The border control, announced on Saturday evening, is on top of new restrictions imposed by the federal government on Saturday, closing the border to nine countries in southern Africa.
Australian citizens entering NSW who have been in South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia, Eswatini, Malawi, and the Seychelles in the last two weeks must now do two weeks of mandatory hotel quarantine, federal Health Minister Greg Hunt announced on Saturday.
Anyone already in NSW who has been in those regions within the previous 14 days must immediately be tested, isolate for 14 days and contact NSW Health.
The NSW measures apply more broadly to anyone who has been overseas at all.
The home quarantine requirement is more extensive for flight crews who have been overseas.
They will have to isolate for 14 days or until they leave the country.
NSW is so far the only jurisdiction to impose extra restrictions on overseas arrivals who haven't been in southern Africa.
"Authorities around the world are still investigating the risk posed by this new variant," Mr Perrottet said.
"The NSW government will continue to put community safety first by taking these precautionary but important steps until more information becomes available."
The new changes kick in at midnight on Saturday.
No cases of the Omicron variant have been detected in NSW, but Health Minister Brad Hazzard said it's concerning as it could be more transmissible than the Delta strain.
"One of the problems with this highly contagious virus, in any of the variants, is that it tends to be out hidden in the community and then announces its presence when we least expect it," he said.
Mr Hazzard said people should consider wearing masks even where the rules do not currently require it, especially when they are near large groups.
Mr Perrottet said there would be no immediate changes to NSW's reopening roadmap.
He warned against complacency, reiterating the pandemic is far from over.
Health experts around the world are working to understand the new variant, which has a higher number of spike protein surfaces.
In particular, Mr Hazzard said, it is not yet known if vaccines are any less effective against the strain.
Meanwhile, the state added 235 new infections to its caseload on Saturday, and no further deaths.
NSW's hospitals continue to treat 174 patients, 26 of them in intensive care units and 10 requiring ventilation
Testers processed more than 62,000 results in the 24 hours to 8pm on Friday.
NSW is 94.5 per cent single-dosed for everyone 16 and over, while 92.3 per cent are fully vaccinated.
Of 12-15-year-olds, 81.2 per cent have received one jab and 76.2 per cent both.
Should NSW reach its goal of 95 per cent full coverage by December 15 an early easing of restrictions will trigger, according to the state's roadmap out of lockdown.
Australian Associated Press