Queensland will ban people from Greater Sydney from travelling to the state from this weekend (July 30).
Premier Annastacia Palaszczuk made the announcement on social media as the number of coronavirus infections in New South Wales grew.
She said: "Queensland will close its borders to all of Greater Sydney. From 1am Saturday, more hot spots will be declared and no one from Sydney will be allowed into Queensland.
"Queensland residents returning will have to isolate in a hotel for 14 days at their own expense."
BREAKING: Queensland will close its borders to all of Greater Sydney. From 1am Saturday, more hotspots will be declared and no one from Sydney will be allowed into Queensland. #COVID19au pic.twitter.com/044iZeTZ1g- Annastacia Palaszczuk (@AnnastaciaMP) July 29, 2020
She added in a press conference: "We are in extraordinary times at the moment and we have to do everything we can."
Queensland has just recorded new coronavirus cases after two people who had travelled from Melbourne to Sydney then Sydney to Brisbane tested positive. They were out in the community for eight days before they got their results back.
Queensland Health Minister Steven Miles said in a press conference: "These young women have gone about their business within the communities that they live in and so there will be a large amount of contact tracing to be done, largely within it the Logan and Springfield areas, including shopping malls, restaurants and a church.
"Our contact tracers are doing that work right now. There is also a number of close contacts in both of their households. That will now be ordered to quarantine."
The news to shut the border to people in Greater Sydney came as a surprise to her southern counterpart, New South Wales Premier Gladys Berejiklian, who confirmed she had no prior knowledge that a large portion of her residents were going to be banned.
"I note that the cases they have had up there, announced today are all from Victoria. And the case from South Australia is from Victoria," Ms Berejiklian said.
"That's a decision for her and in the end, it hurts the smaller states when they don't interact with NSW. It hurts us less if you talk about economy and that's a decision for her."
"The economic consequences in Queensland or South Australia will hurt much more than it hurts NSW, we are in the strongest position in the nation, which we want to maintain obviously."
Queensland had already banned people in Sydney, but only from coronavirus hotspot areas.
Announced on July 10, people living in Campbelltown LGA in western Sydney, Fairfield City in western Sydney and Liverpool LGA in south west Sydney weren't permitted to travel. However, that has now been expanded to include the whole city.