Queensland will close its border to all of New South Wales and the ACT from 1:00am on Saturday.
It comes as the state recorded one new case of coronavirus.
The 68-year-old Queensland woman was diagnosed with the virus in the past 24 hours and authorities are still investigating the source of the infection.
Two historic cases have also been added to the state’s total of 1,088 cases.
The hotspot declaration means anyone travelling from NSW or the nation’s capital will soon be banned from entering the Sunshine State.
Queenslanders who return after travelling there will be sent to mandatory hotel quarantine for 14 days at their own expense.
‘We cannot risk a second wave’
Premier Annastacia Palaszczuk said she was increasingly concerned about community transmission rates in southern states.
“We cannot risk a second wave. We have to act decisively,” she said.
“We have to put Queenslanders first.”
The move means New South Wales and the ACT will join Victoria on Queensland’s list of declared coronavirus hotspots.
Ms Palaszczuk said her decision was influenced by a number of people who had breached the state’s border requirements, by lying to authorities about their whereabouts.
“This is the right decision for Queensland,” she said.
“We cannot put Queenslanders at risk — it is too important.”
For the latest news on the COVID-19 pandemic read our coronavirus update story.
The Premier said losing tourism from the southern states would be difficult, but it was a minimal drawback compared to the economic pain expected from a second wave.
“It is going to be tough for some of our small businesses in some of those communities,” Ms Palaszczuk said.
“But what would be more catastrophic is to take Queensland backwards.
“My job is to protect Queenslanders Health and to protect our economy and our lifestyle.”
Border crossing checks to be stepped up
The declaration comes as Queensland police closed an investigation into a security guard who was granted an exemption before testing positive to coronavirus, saying the man “did nothing wrong”.
Meanwhile, COVID-19 test results for three Logan men, who allegedly lied about having been to a coronavirus hotspot when re-entering Queensland at the weekend, have returned negative.
The men will be tested a second time.
The trio remain in hotel quarantine in Brisbane.
Deputy Police Commissioner Steve Gollschewski said he had evidence people were travelling from COVID-hotspots into other areas such as Canberra, to flout border restrictions.
“We’re currently investigating a male person who we will allege … has deliberately driven from Sydney out of a hotspot into the ACT to get a flight to come to Brisbane and then connected into Cairns, ” he said.
“And that person has expressed they were frustrated with the restrictions, didn’t like them and wanted to go to work — so a quite selfish approach.”
Police have also charged two other people, a man and woman in their 60s, with falsely declaring they had not travelled to a COVID-19 hotspot.
Officers on Tuesday detained the couple in Nanango, north of Toowoomba, after receiving information that they had allegedly travelled through the Goondiwindi police checkpoint with false declarations on July 27.
Health Minister Steven Miles said border protections would be stepped up, forcing visitors to show photo identification to verify their credentials.
He also urged Queenslanders to get home before the weekend lockdown.
“If you’re a Queenslander in New South Wales, please come home,” Mr Miles said.
“If you’re a Queenslander who has any plans to travel to New South Wales, please change those plans now.
“Anyone else travelling to Queensland and allowed to continue to travel to Queensland will have to travel by air or via the Northern Territory border.
“They will not be able to travel into Queensland via the Queensland/New South Wales border.”
Mr Miles said the border closures would be reviewed at the end of August.
Border measures ‘haven’t been handled well’
Opposition Leader Deb Frecklington took a swipe at the State Government’s handling of the border control measures, but backed the new closure.
Ms Frecklington said the Government had mishandled border checkpoints, which had resulted in the boundary needing to be closed to New South Wales for a second time.
She denied changing her position on the issue, although the LNP pressured the Government to open the border early during the original closure.
“Now let’s remember, it was the Premier who then opened the borders and we’re in this circumstance because it has become increasingly clear that the border control measures haven’t been handled very well by the Palaszczuk Labor Government,” she said.
“We know that the situation has changed in Victoria and New South Wales, so we do support the tougher measures to keep Queenslanders safe and to protect their lives and livelihoods.”