NSW Police defend 'lamentable' advice to Jewish community ahead ...

NSW Police has launched an investigation into the behaviour of protesters at a pro-Palestinian rally outside the Sydney Opera House where flares were set off.

Key points:Assistant Commissioner Tony Cooke says it was the 'best option' to manage the protest An operation into the use of flares at the protest has been establishedOne man was arrested at Town Hall and released soon after for unfurling an Israeli flag

The rally began in central Sydney to show support for the Palestinian people after Hamas militants killed hundreds of people in Israel and Israeli forces responded by launching a barrage of rocket fire on Gaza.

Gaza's Health Ministry said at least 687 Palestinians had been killed.

After speeches at Town Hall on Monday evening, the gathering moved to Circular Quay and the Sydney Opera House forecourt where police said the crowd swelled to about 1,000 and flares were lit.

NSW Police Assistant Commissioner Tony Cooke said police became aware of the rally on Sunday and on Monday found out the intention of the organisers was to move through the city.

"In the circumstances, it was considered the best option for police was to manage the movement of those people from Sydney Town Hall to the Opera House," he said.

Police Minister Yasmin Catley said the group did not fill out the necessary paperwork and police did not approve the march.

"The process for avoiding protest meetings or marches — known as Form 1 — generally takes about a week to complete. There was no Form 1 for this event," she said.

No arrests over Sydney Opera House gathering

A man holding an Israeli flag was arrested while attending the rally at Sydney's Town Hall.

Assistant Commissioner Cooke said the decision to arrest the man was made for his safety.

"He was arrested to prevent a breach of the peace for his safety. He was removed and released," he said.

The protesters set off flares and fireworks on the forecourt of the Opera House.(ABC News: Sean Tarek Goodwin)

Assistant Commissioner Cooke said while no-one has been arrested over the use of flares at the rally, the behaviour of those in the crowd was under investigation.

"You could see from the footage that people were very agitated," Assistant Commissioner Cooke said.

"The entire rally and footage was covered by CCTV footage and an operation has been established to look into the issues last night.

"We will attempt to identify people who committed offences and will take appropriate actions to put them before the courts."

In a statement on Facebook, organisers of the event Palestine Action Group Sydney said it was a peaceful rally and there was a "tiny fringe of vile anti-Semitic attendees" who joined their demonstration and chanted phrases including "f... the Jews".

Protest organiser Fahad Ali said the chants were "distressing" to Jewish and Christian allies who attended the rally.

"Our comrades, our friends, and our fellow people of all diverse backgrounds certainly can’t feel good about this, and we have an obligation to call out this behaviour when we see it.

"Last night there was a contingent organised by a group called Jews Against Oppression and Palestinian Christians, so when the minority of individuals decided to centre themselves at the expense of the broader protests that was very distressing."

Mr Fahad said he approached people in the crowd who made the comments and told them to leave.

"We have consistently taken an anti-racist stand and Palestinian liberation is an anti-racist movement," he said.

"What is happening now is there has been a lot of media attention diverted from the suffering of people in Gaza."

Police advice to Jewish community 'lamentable'

Prime Minister Anthony Albanese earlier called for the march to be abandoned, saying the killing and capture of innocent civilians should be condemned.

Federal Opposition Leader Peter Dutton said the prime minister should have spoken to community leaders to avoid the protest from being held.

Rows of police monitored the situation.(ABC News: Sean Tarek Goodwin)

Assistant Commissioner Cooke said it was not the police's position to stop protests and confirmed he spoke to members of the Jewish community "numerous times" before the protest to avoid people putting themselves at "significant risk".

"It was considered the best option for police was to manage the movement of those people," he said.

"This is not about us condoning, supporting, facilitating any process ... This is about us providing for the public safety."

Executive Council of Australian Jewry co-head Alex Ryvchin said the police advice for the Jewish community was "lamentable" but accepts police were doing what they thought was necessary to protect people.

"I bear no grievances towards them but I think it's a lamentable state of affairs when you have members of the Jewish community in the city unable to go to our CBD unable to gather and rally to observe an act of solidarity such as this," he said.

"The fact that the mobs, those who preach violence and intimidation and harassment and racism have dominated the streets in such a way I think is a shocking state of affairs."

NSW Premier Chris Minns defended police handling of the protest but changes would be made to ensure members of the Jewish community could gather safely in future.

Australia's former ambassador to Israel Dave Sharma told ABC News Breakfast it was a "failure" that members of the Jewish community were not able to go to the opera house last night to see its sails lit up in the colours of the Israeli flag.

"This march should not have been allowed to go ahead last night, and certainly not on the route that it had planned," he said.

"They should have found another location or another evening for that to happen."