Public Health Director Dr Mark Veitch said these areas were being declared as high-risk following additional cases in New South Wales.

"If you are in Tasmania now and were in any of the newly designated high-risk areas on or since 21 June you should self-isolate immediately and get a COVID-19 test at least five days after you left Sydney," he said.

People can come out of isolation once they receive a negative COVID-19 test result.

The requirement is set to cause higher than normal demand on the hotline and testing clinics, with Dr Veitch urging for patience.

People currently in home or hotel quarantine in Tasmania because they had visited one of the high-risk areas on Wednesday June 23 are still required to complete those requirements.

Anyone who has been in any of the newly designated high-risk areas since 21 June will not be permitted to enter Tasmania unless approved as an essential traveler by the deputy state controller.

Returning Tasmanians will need to apply to re-enter Tasmania and will be required to quarantine in a suitable premises for 14 days.

A large number of premises in NSW have also been declared as high-risk by the Tasmanian Director of Public Health.

The list of premises is available at www.coronavirus.tas.gov.au/travelalert. It will be updated several times a day.

Dr Veitch said anybody who is currently in Tasmania but has been in NSW since June 11 should continue to check the list.

Anyone who is planning on travelling to Tasmania who has been to any of these high-risk premises at the specified dates and times will not be permitted to enter the state.

Anybody with even the mildest cold or flu symptoms are urged to self-isolate and contact Public Health on 1800 671 738 to arrange a test.

EARLIER:

Tasmanian borders are set to close to Greater Sydney this afternoon for a yet-to-be-determined period of time.

Premier Peter Gutwein said the deputy State Controller and Public Health Director are currently meeting to determine what the situation would look like.

"I've been advised that as of 4pm, we'll be putting in place border restrictions with Greater Sydney, Woollongong is also being considered," Mr Gutwein said.

"The Director of Public Health will have more to say shortly in terms of the arrangements for that.

"Just to be clear- in terms of the worsening situation in New South Wales, from 4pm this afternoon there will be border controls put in place for Greater Sydney."

Border controls are currently in place with seven local government areas in New South Wales - this set to expand that number to more than 30.

People are encouraged to visit coronavirus.tas.gov.au to view a map of affected areas.

Full details are expected this afternoon from Public Health.

This comes as Greater Sydney, the Blue Mountains, Central Coast and Wollongong goes into a 14-day lockdown from 6pm to get on top of the rapidly growing outbreak it currently faces.

IN OTHER NEWS:

"The NSW government has always prided itself on taking the expert health advice," Premier Gladys Berejiklian said after a crisis cabinet meeting where the decision was made.

"Even though we don't want to impose burdens unless we absolutely have to, unfortunately, this is a situation where we have to."

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