Julian Assange joins pro-Palestine march across Sydney Harbour Bridge before police stop rally citing safety fears | Sydney Harbour Bridge

Tens of thousands of pro-Palestine marchers, including Julian Assange, Bob Carr and Ed Husic, have marched across Sydney Harbour Bridge in the rain to protest against Israel’s conduct in Gaza and to speak out about the children starving there.

The world-famous landmark was closed to traffic at 11.30am on Sunday, with protesters gathering in Lang Park in the city centre in chilly weather before walking north to Bradfield Park across the bridge.

About 3pm, NSW police sent out a mass text message to phones throughout the city ordering the pro-Palestine march to stop due to safety concerns, with authorities turning protesters around at the north end.

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“Message from NSW Police: In consultation with the organisers, the march needs to stop due to public safety and await further instructions,” the message read.

A police helicopter hovered overhead with instructions for the hordes of protesters to turn around and walk back towards the city.

A second text message read: “After consultation with the protest organisers, we are asking that everyone stops walking north. As soon as the march has stopped, we will look at turning everyone around back towards the city BUT it needs to be done in a controlled way in stages to keep everyone safe.”

Crowd estimates varied. A spokesperson for rally organiser Palestine Action Group said police had informed them 100,000 people were in attendance – but the spokesperson estimated the figure was closer to 300,000.

Earlier, the Indigenous actor Meyne Wyatt and the former Socceroo and Australian of the Year Craig Foster were among tens of thousands of people marching in the wet weather, while the Greens senator Mehreen Faruqi spoke passionately before the walk began.

Faruqi, who has been an outspoken critic of the federal government’s action in relation to Israel’s conduct in Gaza, commended protesters for “defying Chris Minns” after the New South Wales premier said: “We cannot allow Sydney to descend into chaos.”

“Thank you for defying Chris Minns,” she said. “This is a man who wants you to stay home and be silent in the face of a genocide.

“It was never about logistics. It was never about traffic. It was never about communications or anything else. It was always about stopping us and silencing us. It was always about protecting Israel and the Labor government from accountability.”

Police had rejected an application from organisers for them to facilitate the march, arguing there was not enough time to prepare a traffic management plan and warned of a potential crowd crush and huge disruptions.

But on Saturday the NSW supreme court ruled the march could go ahead.

On Sunday protesters turned out carrying pots and pans – to highlight the starvation in Gaza – while many carried Palestinian flags and signage along with their wet weather gear and umbrellas.

One protester that Guardian Australia spoke to, a British man called Dan, held a sign reading “Gay Jews 4 Gaza”.

“I grew up in a north London Jewish community, and I think there’s a widespread Zionism that exists within the Jewish community that is difficult to separate from religion,” he said, adding: “I think it’s important for people within the community to stand up and raise their voice against the state of Israel because they’re not representative of the Jewish community as a whole.”

Guardian Australia also spoke to Philomena McGoldrick, a registered nurse and midwife, who has spent stints working in Gaza and described her heartbreak at images circulating of starving children.

“Innocent babies have no colour, no religion, no language. In this day and age … it’s heartbreaking … But it’s nice to meet people standing on the right side. The tide has changed.”

The WikiLeaks founder was also spotted in the crowd, one of few public appearances since Assange arrived home in Australia after a decade-long extradition battle.

He was photographed alongside Carr, the former NSW premier and federal foreign affairs minister who last week told Guardian Australia the federal government should sanction the Israeli prime minister, Benjamin Netanyahu, and move quickly to recognise Palestinian statehood.

Carr said it would send “a message that we are turned inside out with disgust by what appears the deliberate starvation” of Gaza.

Carr’s call was echoed by Husic, a federal Labor MP and former cabinet minister, who joined the rally to march across the bridge alongside the five state Labor MPs who defied Minns.

“People power has come out, I think, largely because they just cannot abide the treatment that has been seen of little kids,” Husic told Guardian Australia after the march.

He reiterated calls for the Albanese government to sanction Israel and join the UK, Canada, and France in recognising Palestinian statehood.

Labor’s Stephen Lawrence, Anthony D’Adam, Lynda Voltz, Cameron Murphy and Sarah Kaine were among 15 NSW politicians who signed an open letter on Thursday evening calling on the government to facilitate “a safe and orderly event” on Sunday.

Meanwhile, pro-Palestinian protesters in Melbourne’s city centre, who had planned to shut down King Street Bridge in solidarity with the Sydney protest, appeared to have been blocked from crossing the bridge.

Video shared on social media by the protest organisers showed police in riot gear and shields blocking the bridge with trucks.

Victoria police were approached to confirm the bridge had been shut down; a spokesperson said a statement would be released at the end of the day.

In Sydney, Transport for NSW urged people to avoid non-essential travel around the central business district and northern parts of the city.