A father and son killed 15 people in a mass shooting that targeted a Jewish celebration on Australia's famed Bondi Beach, police said on Monday in an updated toll that included a 10-year-old girl.

One of the gunmen – a 50-year-old man – was shot and killed by police, while the other suspect is his 24-year-old son, who was critically injured and had been taken to hospital under police guard.

"I can say that we are not looking for a further offender," New South Wales police commissioner Mal Lanyon told a news conference.

Some 40 people were injured after two gunmen opened fire at a Jewish event on Sunday evening marking the start of the Hanukkah festival.

"Five people remain in critical conditions with the others remaining in serious and stable conditions," New South Wales Police said in a statement.

Police have declared the shooting a "terrorist incident" and said they had found suspected "improvised explosive devices" in a vehicle near the beach.

The shooting took place during an annual Hanukkah event at Bondi Beach. which police said was attended by over 1,000 people.

Authorities said far more people would have been killed were it not for a bystander, identified by local media as fruit shop owner Ahmed al-Ahmed, 43, who was filmed charging a gunman from behind, grappling with him and wresting a rifle from his hands.

"There are many, many people alive tonight as a result of his bravery," said Chris Minns, premier of New South Wales state where Sydney is located, calling the bystander "a genuine hero".

Prime Minister Anthony Albanese convened a meeting of the country's national security council and condemned the attack, saying the evil that was unleashed was "beyond comprehension".

"This is a targeted attack on Jewish Australians on the first day of Hanukkah, which should be a day of joy, a celebration of faith," he said.

"At this dark moment for our nation, our police and security agencies are working to determine anyone associated with this outrage."

Witnesses said the shooting at the famed beach, which was packed on a hot summer's evening, lasted about 10 minutes, sending hundreds of people scattering along the sand and into nearby streets and parks.

"We all panicked and started running as well. So we left everything behind, like flip-flops, everything. We just ran through the hill," said Bondi Junction resident Marcos Carvalho, 38, who had been packing up after a day at the beach when he heard what he estimated were 40-50 gunshots.

Bondi resident Grace Mathew said people ran past her and she heard gunshots.

"Initially you just think, it's a beautiful day down by the beach," she said. "You sort of think that people are just having a good time. Then more people ran past and said there's a shooter, there's a mass shooting and they're killing people."

Sunday's shootings were the most serious of a string of antisemitic attacks on synagogues, buildings and cars in Australia since the beginning of Israel's war in Gaza in October 2023.

Australia's Jewish diaspora is small but deeply embedded in the wider community, with about 150,000 people who identify as Jewish in the country of 27 million. About one-third of them are estimated to live in Sydney's eastern suburbs, including Bondi.

"If we were targeted deliberately in this way, it's something of a scale that none of us could have ever fathomed. It's a horrific thing," Alex Ryvchin, co-chief executive of the Executive Council of Australian Jewry, told Sky News, adding his media adviser had been wounded in the attack.

Mass shootings are rare in Australia, one of the world's safest countries. Sunday's attack was the worst since 1996, when a gunman killed 35 people at a tourist site in the southern state of Tasmania. (Agencies)