'Stop this genocide': plea for lasting Gaza ceasefire

Tens of thousands of protesters around Australia have voiced concerns over a ceasefire holding in Gaza without further bloodshed as pro-Israel supporters await the exchange of Hamas-held hostages.

Among the pro-Palestine protesters that turned up in capital cities were Australians back home after being detained in Israel for seeking to deliver aid to Gaza during a naval blockade.

Juliet Lamont, whose boat reached 32km off Gaza's coast, said Prime Minister Anthony Albanese needed to distance the country from "the Trumpian bully-boy death cult".

Her colleague Abubakir Rafiq held back tears as he recounted being held in a cell with 83 other men in Ketziot prison in Israel and drew attention to thousands of Palestinians inmates in Israeli jails.

"What about the 10,000 Palestinian hostages that are being held in prisons? Innocent mothers, innocent children, innocent fathers that have been stripped of their rights," he told the crowd.

Mr Rafiq lambasted Foreign Minister Penny Wong for repeatedly denying Australia was participating in delivering arms to Israel including parts for F-35 jets used in the two-year bombing campaign in Gaza.

"What non-lethal part is there of a fighter jet? We are manufacturing weapons that are taking the lives of innocent children," he said.

Shamikh Badra, a University of Sydney political science PhD student originally from Gaza, was worried for the safety of his elderly mother and the rest of his family.

"We don't want a temporary ceasefire, we want to stop this genocide after two years of suffering and two years of watching and worrying" he told AAP as protesters banged on drums and waved Palestinian flags.

An independent United Nations panel in September found Israel had committed genocide in Gaza over the last two years.

Mr Badra's brothers and several members of his family, including children, were killed. He does not know where their bodies are buried in the rubble.

"What if my family in Khan Younis move again and the bombing starts again. Perhaps it will be more dangerous than before."

Despite the NSW Court of Appeal prohibiting a rally at the Sydney Opera House, the protesters headed down George Street to Belmore Park and others marched in Melbourne, Brisbane and Perth.

Police said about 8000 people had marched in Sydney with several helicopters surveying the crowd.

A 30-year-old was arrested after being found in possession of an offensive implement.

Wearing a sling for his injured arm Surya McEwen, 40, another aid activist detained by Israel, said his treatment and that of his peers paled in comparison to what Palestinians endure by Israeli prison guards.

"We had the five-star western passport treatment ... so a broken rib and a dislocated arm are our subtle versions of abuse (that) is nothing compared to what Palestinian experience who are being tortured to death," he told AAP.

He had serious reservations about the ceasefire, which came into effect on Saturday, not being violated.

"Anytime there's a pause in fighting, Israel kills Palestinians and it has not stopped. It and the US are not honest brokers," he said.

Israel launched a two-year military offensive on Gaza that killed more than 67,000 people including about 20,000 children, according to the United Nations.

It came after militant group Hamas launched a surprise attack on Israel which reportedly killed 1200 people, with more than 250 taken hostage.

At a solemn vigil in eastern Sydney organised by Jewish groups, thousands gathered praying for the repatriation of 20 remaining hostages with a cantor reciting a prayer commemorating those killed.

Israeli ambassador Amir Maimon paid tribute to the resolve of survivors of the October 7 attack but the crowd booed loudly when he mentioned Mr Albanese and Ms Wong.

By contrast former Aboriginal athlete and politician Nova Peris received a warm welcome as she emphasised the links between her Christian faith, Aboriginality and Jewish people.

She criticised the government's recognition of the state of Palestine saying it occurred "under the shadow of blood, yet us Aboriginal people here at home, we are still waiting for recognition."

Ms Peris also took aim at pro-Palestine supporters.

"Israel is not going anywhere nor are her people," she said to loud cheers from thousands of attendees.