Australian authorities are taking legal action to try stop a Black Lives Matter protest scheduled to take place in Sydney on Saturday, citing the risk of an outbreak of COVID-19 given the large numbers expected to attend.

Australia has reported daily single and low double digit numbers of new COVID-19 cases in recent weeks and has 490 active cases, with just 25 people in hospital.

The last-minute move by the New South Wales state government on Friday came after Prime Minister Scott Morrison told people not to attend the gathering and similar rallies in Melbourne and other major cities.

Morrison has warned against "importing the things that are happening overseas to Australia" during a radio interview on Thursday. He acknowledged that Australia has the problem of racism, but added that, "We don't need the divisions that we're seeing in other countries – we need to stick together and look after each other," Morrison told 2GB.

NSW police had originally approved the protest, as it originally planned to have fewer than 500 people present. But State Premier Gladys Berejiklian said when it became clear that thousands planned to attend, the legal application was made to the state's Supreme Court.

"The New South Wales government would never, ever give the green light to thousands of people flagrantly disregarding the health orders," Berejiklian told reporters in Sydney.

The NSW Supreme Court will hear the matter on Friday afternoon.

Morrison said earlier that people should find other ways to express anger following the death of black American George Floyd.

"The health advice is very clear, it's not a good idea to go," he told reporters in Canberra. "Let's find a better way and another way to express these sentiments ... let's exercise our liberties responsibly."

The Melbourne protest is still scheduled to take place with state police approval, although Victoria State Premier Daniel Andrews has urged people not to attend.

The protests will also throw a spotlight on police treatment of Australian indigenous people, including the deaths of Aboriginal men in custody.

(With input from Reuters)