The death toll from Sunday's mass shooting at a Jewish holiday celebration on Sydney's Bondi Beach rose to 16, police said early on Monday.

Police said in a post on X that 16 people had died and 40 people remained in hospital following the shooting. The post did not specify whether the suspected gunman initially killed on Sunday was included in that toll.

A second gunman was in critical condition and police were investigating whether a third attacker was involved, New South Wales Police Commissioner Mal Lanyon told a press conference. Two police officers were among the people taken to the hospital with injuries, he said.

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."

A bomb-disposal unit was working on several suspected improvised explosive devices, Lanyon said. Mike Burgess, a top Australian intelligence official, said one of the suspected attackers was known to authorities but had not been deemed an immediate threat.

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. Police said around 1,000 people had attended the Hanukkah event.

"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.

"Antisemitism has no place in this world. Our prayers are with the victims of this horrific attack, the Jewish community, and the people of Australia," U.S. Secretary of State Marco Rubio wrote on X.

Israeli Prime Minister Benjamin Netanyahu called the attack "cold-blooded murder," and said he had warned Albanese about antisemitism before Australia, along with Britain, Canada and France, recognised a Palestinian state in September.

"Your call for a Palestinian state pours fuel on the antisemitic fire. It rewards Hamas terrorists. It emboldens those who menace Australian Jews and encourages the Jew hatred now stalking your streets," Netanyahu said he had written to the Australian leader in August.

The Australian National Imams Council condemned the shooting in a statement: "These acts of violence and crimes have no place in our society. Those responsible must be held fully accountable and face the full force of the law."