South Australian authorities are "extraordinarily concerned" about the Omicron COVID-19 variant's presence interstate, but will not make any immediate changes to the state's borders.
But Queensland has announced arrivals from Greater Adelaide will be required to go into home or hotel quarantine from 1am Sunday, 5 December.
Greater Adelaide arrivals to Queensland after 1am on Monday 6 December will need to have received a negative COVID-19 PCR test result in the 72 hours prior to arrival.
Queensland Chief Health Officer Dr Peter Aitken said the decision followed the detection of multiple COVID-19 cases connected to a school reunion in Adelaide, and multiple high risk exposure sites being linked to those cases.
It came as the state recorded five new cases of COVID-19 - a male in his 50s, three females in their 30s, 50s, and 60s, and one child.
Three of the new cases are linked to the Norwood cluster.
SA Premier Steven Marshall indicated travellers from NSW, Victoria and the ACT could soon find themselves locked out of SA, only days after they were welcomed back for the first time in months.
"It may become necessary. I hope it doesn't," he said in a press conference on Saturday morning.
"We would only do that if we wanted to make sure that we still enjoy a Christmas here in SA. This is a balancing act."
Instead of announcing immediate changes to the border regime, Mr Marshall said the state's COVID-19 directions committee had decided to require all arrivals from NSW, Victoria and the ACT be tested upon arrival.
They must isolate until a negative result is received, and be tested again on day six of their visit to SA.
The new rules are in addition to a requirement for travellers from those states to present proof of a negative test undertaken up to 72 hours before their arrival.
"We're going to put as many speed bumps in the way of the Omicron variant while we gather more information as to whether or not this really is a very different situation going forward," he said.
The premier rejected suggestions the government was being indecisive on borders.
The state is managing the transmission of the Delta COVID-19 variant as expected, but Omicron is a "game changer" he said.
"This has got nothing to do with Delta it has got everything to do with the Omicron variant," Mr Marshall said.
"We remain extraordinarily concerned about the Omicron threat."
South Australia this week reported its largest single-day tally for more than a year, with the current outbreak forcing the governor and the opposition leader into isolation.
Queensland, meanwhile, recorded seven new cases of COVID-19 on Saturday.
Two were acquired overseas in hotel quarantine, two were from interstate and three were acquired locally.
Four of the cases had been infectious in the community, including a Gold Coast couple who were infectious for up to 13 days, Health Minister Yvette D'Ath said
One infection is linked to the school reunion in SA.
Testing is underway into whether the new cases are of the Omicron variant.
Victoria, NSW updates
Meanwhile, Victoria on Saturday recorded 1,365 new infections and nine more deaths.
The state continues to manage almost 14,400 active coronavirus cases. There are 288 virus patients in Victorian hospitals, 44 of them in intensive care and 20 requiring ventilation.
Thousands of people in the first mass demonstration since the state government passed pandemic laws.
A counter-protest against far-right elements of the so-called 'freedom protests' was also set to take place.
And in New South Wales, authorities are racing to track down the source of an emerging Omicron variant cluster at a Western Sydney school as COVID-19 case numbers begin to spike again.
The state reported another 325 new cases of the coronavirus on Saturday, and one death, 12 fewer than the number reported on Friday, which was the highest tally in six weeks.
There have been 13 Omicron cases confirmed with genomic testing in NSW since the first cases were reported on Sunday, but only about half are linked to the eight countries of concern.
A concerning cluster of infections at Regents Park Christian School in Western Sydney stands at 13, with three already confirmed positive for Omicron. Testing results are still to come for the other 10.
The first student confirmed to have the new variant did not have any known link to southern Africa and urgent investigations are searching for the source of the cluster.
The cluster has now also been linked to the Sydney Indoor Climbing Gym in Villawood. Anyone who attended the gym last Saturday, November 27, between 9am and 4.30pm is a close contact and must immediately get tested and isolate.
The ACT on Saturday reported seven new local cases, one suspected to be Omicron, while the Northern Territory recorded none.
