Thousands of protesters will push ahead with Black Lives Matter rallies on Saturday as the prime minister and other leaders warned against the mass gatherings and NSW’s highest court banned Sydney’s demonstration.

NSW Supreme Court Justice Des Fagan on Friday declared the Stop All Black Deaths in Custody rally, organised by activist Raul Bassi, was not an authorised public assembly.

“The exercise of the fundamental right of assembly … is not taken away by the current public health order, it is deferred,” Justice Fagan said.

About 5000 people were expected to rally at Sydney Town Hall in honour of US man George Floyd and Australian David Dungay Jr., an Aboriginal man who died in prison in 2015.

David Dungay, 26, died in Long Bay hospital in 2015.

Rallies are also scheduled for Melbourne, Brisbane, Adelaide and Hobart, with Victorians warned they could be arrested for attending the march.

Organisers have urged people to follow social distancing regulations by demonstrating in groups of 20 and to stand 1.5m apart while following other pandemic safety measures such as using hand sanitiser.

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However Australia’s Chief Medical Officer Brendan Murphy said authorities feared an outbreak in indigenous communities where people are more vulnerable to COVID-19.

Prime Minister Scott Morrison urged people to find another way to protest as he warned the mass gatherings could risk rewinding Australia’s gains against the spread of the coronavirus.

As countries around the world remain in the grip of their own outbreaks, world leaders have issued similar warnings against people taking to the streets and risking further spread of COVID-19.

UK health secretary Matt Hancock said it was vital to avoid George Floyd protests as deaths in his country passed 40,000, only the second country after the US to reach that milestone.

In Paris, French police banned a demonstration planned outside the US Embassy, citing the risks of social disorder and health dangers.

Donald Trump: ‘Great day’ for George Floyd

Donald Trump has been criticised for his comments on George Floyd during a speech on the economy.

American protesters have vowed to harness the outpouring of support to create a sustained movement as demonstrations that had begun violently in Minneapolis maintained a calmer shift.

But as public gatherings continued for an eleventh day, President Donald Trump unusually named George Floyd in a speech on the nation’s economy.

As he touted the latest jobs report, Mr Trump said it was a ‘great day’ for George.

“We all saw what happened last week. We can’t let that happen. Hopefully George is looking down and saying this is a great thing that’s happening for our country,” he said.

“(It’s) a great day for him. It’s a great day for everybody.

“This is a great, great day in terms of equality.”

Mr Trump’s comments drew immediate criticism as the country faces high unemployment due to the rampant spread of coronavirus as well as an upsurge in racial unrest.

In Minneapolis, where Floyd died in police custody, the city has agreed to ban police chokeholds and require officers to intervene any time they see unauthorised force by another officer.

Australian protests

Australians will march in honour of George Floyd but the rallies are also a show of support to the Aboriginal community to highlight high levels of indigenous incarceration and deaths in custody.

While banning the Sydney rally, Justice Fagan said he appreciated the importance of the event and recognised it was designed to be concurrent with similar events in other countries.

Leetona Dungay (mother of David Dungay Jr) is comforted outside the Supreme Court in Sydney. Photo: AAP

“I don’t diminish the importance of the issues, and no one would deny them in normal circumstances,” he said.

“No one denies them that but we’re talking about a situation of a health crisis.”

Other countries hadn’t respected coronavirus and had suffered “markedly worse” than Australia, he said.

Australians had also surrendered their livelihoods, pursuits, endeavours and rights to worship to help halt the spread of COVID-19, the judge said.

“Everyone has given up a lot in order to defeat the disease on the basis that this is the best advice health officials have given us,” he said.

Organiser Raul Bassi said he and police agreed on Thursday the protest could go ahead.

The state’s Chief Health Officer, Dr Kerry Chant, was among witnesses to give evidence and told the court while there was a low level of community transmission in NSW, an event that large would increase the risk.

“At this current point in time, even despite high rates of testing, there is a possibility we are missing cases in the community,” Dr Chant said.

Modelling on behalf of the commonwealth predicted an “upswing” in cases as COVID-19 restrictions eased, although the modelling did not consider specific events.

Barrister Emmanuel Kerkyasharian, for the organisers, submitted the “safer course” would be to allow the rally with social distancing measures.

– with AAP and ABC