Victoria will enter a five-day lockdown in an effort to contain the Holiday Inn coronavirus outbreak, which now totals 13 cases.
Premier Daniel Andrews confirmed the state will enter the lockdown at 11.59pm tonight.
People will only be able to leave their homes to shop for food and essential items, to provide or receive care, exercise, and work and study if they can't from home.
The 5km limit on travel will also be reimposed, as will the compulsory use of masks both indoors and outdoors.
The Australian Open tennis tournament will continue without crowds.
Mr Andrews said the UK strain of the virus is "so hyper-infectious and moves so fast that it is presenting a very real challenge" for authorities.
"It is the advice to me that we must assume that there are further cases in the community than we have positive results for, and that it is moving at a velocity that has not been seen anywhere in our country over the course of these last 12 months," he said.
Victoria recorded five new Covid-19 cases on Friday, all of which are connected to the Holiday Inn at Melbourne Airport.
The new cases include a female assistant manager and four close contacts of people who earlier tested positive to Covid-19.
The whole of Melbourne Airport's Terminal 4 has been listed as an exposure site after a case worked at Brunetti cafe on February 9 between 4.45am and 1.15pm.
Anyone who visited the terminal during that time needs to get a COVID-19 test and isolate for 14 days, including those who have since travelled interstate.
There are now 19 active cases in total in Victoria, with more than 24,000 tests conducted on Thursday.