Police maintained a presence in marked and unmarked cars on Saturday morning after flyers began circulating yesterday about a gathering to "defend our freedom".

Meanwhile, 20 people have been arrested after about 100 gathered at Melbourne's Shrine of Remembrance.

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An Australian Associated Press photographer said a man punched an officer at the scene before he was fitted with a mask and handcuffs.

It is unclear whether Bendigo's protests were supposed to be genuine, who posted the flyers or what their motivations were.

However, the location of the protest appeared to have one parallel with Melbourne's.

They were to take place next to the Bendigo's Soldiers Memorial Institute which, like the Shrine of Remembrance, could be seen to represent Australian freedom.

The flyers were placed on a number of cars in Kangaroo Flat yesterday.

They invited people to "come and join us tomorrow to defend our freedom ... stand up before it's too late".

Victoria Police issued a statement to the Bendigo Advertiser before the apparent protests confirming it was aware that "some individuals" might have been planning to take part in a protest.

The statement said anyone who attended would blatantly breach the chief health officer directions and put lives at risk.

"Be assured Victoria Police will be responding and will take appropriate action," the statement warned.

"We will have a strong presence, and will take swift action against anyone who is continuing to deliberately breach the current restrictions.

"We will have no hesitation in issuing $1652 fines or making arrests on the day, if necessary."

Uniformed police in unmarked cars parked at Bendigo's courthouse close to 11am, while multiple marked vehicles circled the area.

The area remained devoid of protesters, though several people sat on benches eating food and a bike rider stopped to catch their breath.

Police did not fine, arrest or move any of them on.

- With Australian Associated Press