Tasmania will close its borders to Victoria after midnight, Premier Peter Gutwein has announced.
Mr Gutwein made the announcement on Friday afternoon after Victorian Premier Daniel Andrews announced the state would enter a five-day lockdown.
This is due to a coronavirus outbreak linked to the Holiday Inn quarantine hotel at Melbourne Airport.
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There are 13 coronavirus cases associated with the hotel; five of which were confirmed on Thursday night.
The first cases identified in the outbreak were confirmed as the more virulent UK strain of COVID-19.
There are 19 active coronavirus cases in Victoria.
Mr Gutwein said all Tasmanians returning to the state after midnight on Friday would be required to undertake 14 days isolation at their own premises, if suitable, or in hotel quarantine.
Hotel quarantine costs would be covered by the government if Tasmanians returned to the state within the first 24 hours of the border closure.
The Brunetti Cafe at Melbourne Airport's terminal four has recently been listed as a high-risk location for coronavirus.
Public Health director Mark Veitch said anybody in Tasmania who passed through the terminal any time last Tuesday would need to self-isolate and arrange testing through the Public Health Hotline.
"We need to be absolutely certain that nobody by chance got infected as they moved through the food court," he said.
Dr Veitch said up to 1000 people in Tasmania could have moved through the food court on February 9.
Mr Gutwein said he would encourage anyone in Tasmania who had been at any of the 28 high-risk locations to self-isolate.
"This is a serious moment for us," he said.
"We are on the cusp of the weekend, the last thing we want is somebody who has been in terminal 4 in that airport, on that particular day ... go out tonight and infect hundreds of people in a nightclub or in a pub."
High-risk locations are listed at www.coronavirus.tas.gov.au/travelalert.
Mr Gutwein said any Tasmanians who had been in those hot spots and returned to the state after midnight on Friday would be required to isolate at a quarantine hotel with costs to be covered by the government.