Western Australia and Tasmania have told tourists it is too late to visit as the number of coronavirus cases in Australia surpasses 2,000.
There are long queues of vehicles at the border between South Australia and WA ahead of its closure at 4pm AEST on Tuesday.
Premier Mark McGowan said even people stuck in cars in the queue would be subject to requirements to self-isolate for 14 days if they enter the state after its closure.
"This is an extraordinary situation and I appreciate it is very difficult at the border. I just ask for patience and understanding as we bring in the new rules to protect the community," he told reporters on Tuesday.
"If you are a tourist and want to come to WA, it's too late. Please don't come."
WA is also planning to restrict movement between regions of the state, advising residents to avoid any unnecessary intrastate travel.
Spirit of Tasmania refuses tourists
Travellers seeking entry into Tasmania face further restrictions with the government warning that those seeking to use the ferry service to enter the state will be turned away in most cases.
Only essential travellers or Tasmanians returning home are allowed to use the TT-Line Bass Strait service, Premier Peter Gutwein announced on Tuesday.
He said the state government is taking a new "hard-line position" for those seeking to use the ferry service.
"As from today, if you are travelling to Tasmania and it's non-essential travel, do not come. Do not get on the TT-Line," he said.
"What we will do is turn you around and ask you to go back."
Hard lockdown considered
Mr Gutwein said a "hard lockdown" of the state is being considered, where only essential services will remain open.
"We're working through those processes," he said.
"I want to say very, very clearly to Tasmanians - if the advice is that we should move to more severe measures, then we will move."
The island state has recorded 28 coronavirus cases, six new ones overnight, but none through local transmission.
Three people who contracted the deadly virus have recovered.
Police to enforce business shutdown
State Sport and Recreation Minister Jane Howlett is in self isolation after her chief of staff was in close contact with a confirmed case of COVID-19.
Ms Howlett had travelled with her staffer to a recent national meeting of sports ministers in Townsville.
The staffer was subsequently contacted by Queensland Health.
Tasmanian Police is setting up "compliance teams" to ensure businesses told to shut are obeying the nationwide order, Mr Gutwein said.
Four of the state's overnight cases were aboard the Ruby Princess cruise ship, one was on the Celebrity Solstice and one had recently returned from overseas.
The World Health Organisation warned overnight that the , with more than 300,000 cases now confirmed and thousand upon thousands of deaths.
If you believe you may have contracted the virus, call your doctor, don’t visit, or contact the national Coronavirus Health Information Hotline on 1800 020 080.
If you are struggling to breathe or experiencing a medical emergency, call 000.
Additional reporting: AAP
