Victoria is going back into lockdown for a third time, State Premier Daniel Andrews has announced.

The embattled Australian state, which just over three months ago came out of a gruelling 15-week lockdown period unmatched the world over, has called a snap lockdown lasting five days.

Stage four restrictions will come into effect at 11:59pm on Friday, and are scheduled to end at the same time next Wednesday.

The restrictions mean Victorians will only be allowed to leave home for one of four reasons: essential supplies, caregiving, exercise or essential work.

Exercise and shopping will be limited to 5km from home, face masks will be mandatory and public gatherings and home visits will be banned. Schools will close but remain available to the children of those who have to go to work.

The move comes after Melbourne Airport's Holiday Inn coronavirus cluster grew to 13 cases on Thursday, with hundreds more people identified as close contacts. These cases are infected with the UK variant of the disease, which is believed to be significantly more infectious. 

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"I am sad to have to report, 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," Andrews told media on Friday afternoon.

"Because it is so infectious, and moving so fast, we need a circuit breaker."

Victorian chief health officer Brett Sutton says the UK variant present in the Holiday Inn cluster is "significantly more infection" than any other form of the virus Australia has seen.

He warns that without this five-day 'circuit breaker' lockdown, the state could see 30 new cases a day by as soon as next week.

"Nobody wants all the consequences of a circuit breaker, but the alternative is potentially devastating," he said.

"I do not want to be here either, come Wednesday, not having done this and talking about 10, 15, 20, 30 new cases a day, including mystery cases, or including cases that we can’t chase down."