Tasmania has closed its border with southeast Queensland and forced some 11,000 recent arrivals from the mainland state into isolation.
The border closure with 11 high-risk local government areas, including Brisbane and the Gold Coast, was implemented from 4pm on Saturday.
Anyone in Tasmania who has been in the high-risk areas since 12.01am on July 17 has been told to stay home.
"If you're in Tasmania, and we expect there are probably about 11,000 people who have travelled into the state, you should immediately go home and isolate," Premier Peter Gutwein told reporters.
The directive is in place until at least 6pm on Tuesday, broadly in line with southeast Queensland's snap three-day lockdown prompted by six new locally acquired COVID-19 cases
People can only leave their houses for grocery shopping, essential services, medical care, exercise within five kilometres, or work or study when it can't be done from home.
"This is not a drill. What has happened in Queensland ... the Delta variant is different. The steps we are taking, we believe, are proportionate," Mr Gutwein said.
Tasmanians in southeast Queensland are allowed to return home but will be forced to quarantine at home or in a hotel.
Tasmania, which hasn't recorded a community virus case since May last year, is also closed to NSW and people who have visited high-risk locations in Victoria and South Australia.
Australian Associated Press