Australian leaders have condemned attacks that wrought the deadliest day in Israel’s history as the conflict entered its third day.

Saturday’s devastating attacks by Hamas militants resulted in more than 700 Israeli deaths, more than 2000 injuries, and at least 100 hostages, the country’s worst death toll from a single assault since 1948.

In response, Israel announced that it targeted more than 1000 sites in Gaza during night-time airstrikes, mobilised military divisions in the southern region, and secured its border with Lebanon.

Fiery protest

In Australia, hundreds of pro-Palestine protesters marched on the Sydney Opera House on Monday evening, setting flares ablaze and chanting in a fiery rally.

Landmarks, including the Opera House, MCG and Parliament House, had been lit up in blue and white to honour Israel’s losses but supporters were warned to stay away because of the protest.

Flares are lit at the Free Palestine rally at the Sydney Opera House. Photo: AAP

Wentworth MP Allegra Spender on Tuesday morning condemned the scenes and chanting as “abhorrent”.

“At a time when there should be solidarity with our Jewish community, they have been subject to appalling abuse,” she wrote on X (Twitter). “I am seeking an urgent explanation of how this was allowed to happen.”

A former Ambassador to Israel, Dave Sharma, told ABC News Breakfast some of the chanting amounted to “racial incitement” and was “despicable”.

Tweet from @spenderallegra

Speaking at the rally, Palestinian and academic Fahad Ali called on the words of anti-apartheid activist Nelson Mandela, saying Palestine had been left with no choice but armed struggle.

“The world has done nothing to support us,” he said.

“Non-violent protest has been criminalised. Governments, including the government of this colonial entity that we call Australia, are tripping over themselves to outlaw boycott, divestment and sanctions on Israel.

Earlier on Monday, Prime Minister Anthony Albanese said the pro-Palestine rally should have been called off out of respect for the loss of life.

“I support people’s right to demonstrate their their views — we’re a democratic nation … But what is to be served apart from creating a climate that is not conducive to peace?” he said.

Declaring himself a supporter of the two-state solution, he also said Hamas’ attack was not in the interests of either Israelis or Palestinians.

“There’s no doubt there has been and continues to be Palestinian suffering but the actions of Hamas in this are completely indefensible,” he said.

“Every effort should always be made to protect and not to harm civilians.

“But Israel, of course, does have a right to defend itself.”

A heavy police presence at the Opera House but no arrests. Photo: AAP

Albanese said Australia had not been asked to provide military aid and condemned the demonstration by the Palestinian Action Group in Sydney.

“What is to be served apart from creating a climate that is not conducive to peace?” he said.

“What we saw on the weekend wasn’t two military forces engaging; this was armed people killing innocent civilians.”

Dutton: No time for restraint

Opposition Leader Peter Dutton also threw his support behind Israel and hit back against foreign minister Penny Wong’s calls for restraint.

“This is not the time for restraint,” he told Sky News on Monday.

“People who try to draw a parallel or argue equivalence between Israeli activity in their retaliation for the strikes and the barbaric attacks that we’ve seen by Hamas —  there is no comparison.”

Israeli Prime Minister Benjamin Netanyahu said the country had moved into the “offensive phase” of the conflict as its aircraft began targeting Hamas strongholds in the Gaza Strip.

The scale of the losses has driven calls for more assertive action, including the deployment of ground forces, not seen since 2014.

“I think Israel is having its 9/11 moment, and whilst that’s a crude simplification it does sort of, I think, help capture how people in Israel are feeling,” said Government Services Minister Bill Shorten.

Deborah Lipstadt, the US special anti-Semitism envoy, termed the attacks “the most lethal assault against Jews since the Holocaust”.

Palestinian casualties have also mounted since Israel started retaliatory airstrikes, with more than 400 killed and 2300 wounded.

Foreign Minister Penny Wong brushed off criticism from Opposition Leader Peter Dutton over her call for restraint from both sides of the conflict.

“We can never condone the targeting of civilians and the taking of hostages,” she said.

On Sunday, a short-lived, cross-border skirmish between Hezbollah militants in Lebanon and Israeli forces stoked fears about the possibility of a broader conflict.

Israeli anger at Netanyahu

Israeli newspaper Haaretz editorialised that blame for the apparent intelligence failure that led to the attack would be laid at the feet of the country’s far-right government.

“The disaster that befell Israel on the holiday of Simchat Torah is the clear responsibility of one person: Benjamin Netanyahu,” the newspaper wrote.

“The Prime Minister, who has prided himself on his vast political experience and irreplaceable wisdom in security matters, completely failed to identify the dangers he was consciously leading Israel into.”

Over the past year, the country’s coalition government has ramped up settlement construction in the West Bank and made moves to curb the power of Israel’s judiciary.

Iran rejected claims that it played a role in the Hamas incursion into Israel on Monday, following reports in the Wall Street Journal that it had helped plan and fund the assault.

In Sydney’s southwest, a Muslim preacher told a crowd gathered in Lakemba on Sunday night, the attacks were an act of resistance.

Dutton said the Coalition “utterly condemns the unprovoked and abhorrent attack by militant Hamas on Israel”.