The Nice attack shows how vulnerable Western nations are to increasingly "creative" terrorists who don't need bombs to kill and create havoc, former prime minister Tony Abbott says.
More than 80 have been killed after a truck was driven into a Bastille Day crowd in the French coastal city. French President Francois Hollande has extended a state of emergency imposed after the Islamic State attacks in Paris last year that killed 130.
Prime Minister Malcolm Turnbull said Australia stood in solidarity with the people of France "in the struggle against Islamist terrorism".
"Only eight months ago we mourned for the victims of terrorist attacks in Paris. Now once again we mourn for the victims of another murderous act of terror in France overnight, on Bastille Day," he said in a statement.
"Our nations are united in freedom's cause today, just as we were a hundred years ago."
Mr Abbott said the truck represented a chilling new tactic, showing terrorists don't need planes, bombs or even guns to launch mass casualty attacks.
"This is the problem. Islamist terrorism - if this is what it turns out to be - has been incredibly creative when it comes to new and even very mundane ways to kill people," he told Fairfax Media.
Mr Abbott says during his time as prime minister he was advised that Australian homegrown terrorists were exploring creative ways to launch attacks here.
"They're always trying to find news ways to create havoc," he said.
The fact Australia had not experienced similar atrocities was a testament to the professionalism of police and security agencies, he said.
"It shows there are people who have nothing but malice towards those who don't share their beliefs," Mr Abbott said. "It shows how vulnerable we are to people who are prepared to kill and be killed without compunction. There's no gratitude to the societies that have given them succour, just malice."Foreign Minister Julie Bishop said her department was providing consular assistance to three Australians caught up in the attack, each who suffered minor injuries while fleeing the area.
Australia's travel advice for France has been updated but the overall level of advice has not changed.
"This latest attack reminds us that no city, no country is immune from terrorist attacks, that's why the Australian government will do all in our power to keep Australians as safe as possible, both at home and abroad," Ms Bishop said.
She said the attack had shook France and "rocked it to its core."
"Australians in Nice should remain attentive to their surroundings, avoid affected areas and follow the instructions of local authorities".
Opposition Leader Bill Shorten said Australians were shocked by the attack.
"Bastille Day has always been an occasion to celebrate the powerful belief the French people have in democracy - the struggle and sacrifice with which they achieved it, and the enduring power of the words liberté, égalité, fraternité.
"These values, infinitely stronger and richer than the hate-filled ideology of those who seek to strike against the French Republic, have stood the test of time. They will prevail."
- with Tom McIlroy
Awful scenes in Nice. Another tragedy inflicted on innocent people. Australia stands with our friends in France.— Bill Shorten (@billshortenmp) July 14, 2016
Shocking reports coming out of Nice. We stand w/ the people of France. Our thoughts are w/ the loved ones of those who’ve died + the injured— Tanya Plibersek (@tanya_plibersek) July 15, 2016