Coronavirus case numbers continue to be in low figures across the state but mystery cases remain a concern, the Chief Health Officer Brett Sutton says.

Mr Andrews pleaded for people to "stay the course" after large groups at beaches and parks flouted virus restrictions in recent days.

"We are so, so close. Let's not any of us do anything that might undermine the very positive numbers," he told reporters on Sunday.

"Once we get them low, we can keep them low and we can open up again

"If we don't do anything silly or anything selfish right now."

Mr Andrews warned people that if they "try to shortcut this thing, then we will be back where we were weeks and months ago".

"Let's not any of us do anything to jeopardise where we find ourselves. It is delicately poised".

Police patrols will continue at St Kilda Beach after large groups gathered on Friday, raising concerns that such behaviour could trigger another outbreak.

"It's sunny, yes, and people love to go to the beach when it's sunny but there's a global pandemic on," Mr Andrews said.

"Surely, there's a greater urge to see this thing, to defeat it and to have a normal summer and have a COVID normal Christmas and 2021."

Professor Sutton said mystery cases remained a concern with an uptick in the 14-day rolling average.

There were 13 mystery cases with an unknown source in Melbourne in the fortnight to October 1, an increase of two from a day earlier.

Three additional mystery cases not included in the latest figures were in the southeast and west of Melbourne in postcodes 3145, 3023 and 3019.

Prof Sutton said a single case of unknown acquisition might represent 10 or 15 true cases in the community.

"It's really a call to arms ... anyone in those postcodes should be aware that there's transmission in those postcodes."

Prof Sutton said outdoor activities were okay but they had to be undertaken safely.

"We know that it is good for emotional wellbeing, psychological wellbeing, so it is important to get out," he said.

But he reminded Victorians that no more than two households or five people can gather and they must maintain social distancing and wear masks.

Health figures released on Sunday show the 14-day rolling average of daily case diagnoses up to Saturday is 11.9 in Melbourne and 0.2 in regional Victoria, up from 0.1 on Saturday.

If Victoria hits a rolling 14-day average below five and a two-week total of below five mystery cases it will move to the third step of reopening by October 19.

There are 241 active cases in Victoria, with 91 in aged care facilities and three in regional Victoria.

The state's death toll is now 806 since the start of the pandemic. The latest death is that of a man in his 80s and linked to an aged care outbreak.

Police said over the last 24-hour period they had issued 104 fines, including 17 for failing to wear a face mask and 11 at vehicle checkpoints

Across Australia, 894 people have died from COVID-19.

Australian Associated Press