Victorians - including those in regional areas - will only be allowed to leave their homes for essential reasons.

These include shopping for essentials, exercise, medical reasons or care-giving, authorised work or education and to get vaccinated.

Victorians must also stay within five kilometres of their homes.

Victorian Premier Daniel Andrews said only a hard lockdown would get the state on top of the current outbreak.

"You only get one chance to go hard and go fast," he said.

"If you wait, if you hesitate, if you doubt, then you will always be looking back wishing you had done more earlier. I am not prepared to avoid a five-day lockdown now only to find ourselves in a five-week or a five-month lockdown.

"That is why we are making this very difficult decision and why I know Victorians will, despite the pain and difficulty of this, know and understand there is no option."

He said regional Victoria may exit the lockdown before Tuesday, pending COVID-19 case numbers.

"I know and understand how frustrating it is for people who don't have, committees and townships that don't have cases and don't have exposure sites to be locked down," he said.

"We will release those parts of Victoria that are safe to release before next Tuesday if it is safe to do so."

The state's fifth lockdown comes after two new stranger-to-stranger COVID-19 cases were announced earlier this afternoon, linked to Saturday's AFL match at the MCG. It takes the current outbreak to 18.

There are 75 exposure sites, 1500 primary close contacts and 5000 secondary close contacts.

More than 6500 people are isolating and three schools are closed.

Thirty new exposure sites have also been added to the list, including two gyms. A positive COVID-19 case attended Persist Fitness in Werribee (July 13) and QuickFit Health Club in Point Cook (July 12-14).

The restrictions follow the reintroduction of face masks in all indoor settings throughout the state, announced yesterday via a late night tweet.

Health authorities continue to race to contain two separate outbreaks after 10 new cases were recorded yesterday, including a teacher from Bacchus Marsh Primary School.

The teacher attended an AFL match between Carlton and Geelong at the MCG on Saturday with a resident of the locked-down Ariele Apartments in Maribyrnong.

Prime Minister Scott Morrison will propose changes to Commonwealth support payments for people and businesses affected by extended COVID-19 lockdowns at a national cabinet meeting tomorrow.

The proposal - originally for New South Wales - is expected to be applied nationally.

Warrnambool and south-west residents can find their closest vaccination centre here.