Victorian health authorities will sit tight during the virus incubation period after more than 10,000 protesters flooded Melbourne's CBD on Saturday

The time estimated for people to develop symptoms, get tested and wait for results will delay knowing whether the mass protest has had any impact on infections.

Encouraging people with symptoms who attended the protest to get tested, Deputy Chief Health Officer Annaliese van Diemen remained 'hopeful' Victoria's case numbers continue to trend downwards.

"If we have no outbreaks in general in two weeks, and we continue to trend downwards, we will see that as a positive in terms of low levels of community transmission," she said.

Many protesters wore face masks while volunteers offered hand sanitiser and encouraged people to practise social distancing.

Organisers, Warriors of the Aboriginal Resistance, had called for protesters to demonstrate in groups of 20 and maintain physical distance of 1.5 metres to not breach coronavirus lockdown laws.

But Victoria Police will fine the Melbourne organisers $1652 each for breaching the directions of the chief health officer amid the pandemic.

The organisers said they were touched by supporters' offers to pay their fines, but preferred the money be directed to families directly affected by deaths in custody.

Premier Daniel Andrews had urged Victorians to avoid attending the protest, asking them to show solidarity with the cause without breaching the chief health officer's restrictions.

Opposition leader Michael O'Brien said the fact that protesters were not fined sent a message that "lockdown doesn't matter anymore".

"For Daniel Andrews to give a free pass to breaches of social distancing rules in the name of social justice has undermined the public health message," he said.

Four new cases of coronavirus in Victoria were reported on Sunday, taking the state's recorded total to 1685.

There are 177 confirmed infections acquired through unknown transmission, and 70 active cases in Victoria.

Australian Associated Press