A father and son appeared to be driven by"Islamic State ideology" when they opened fire on a Jewish festival at Sydney's Bondi Beach, Australian Prime Minister Anthony Albanese said Tuesday.

Sajid Akram and his son Naveed killed 15 people in a mass shooting that targeted a Jewish Hanukkah celebration at the famous beach on Sunday evening.

Authorities have described the attack as an antisemitic act of terrorism, but have so far given little detail on the deeper motivations.

Albanese gave one of the first hints on Tuesday that the pair had been radicalised before committing"mass murder".

"It would appear that this was motivated by Islamic State ideology," Albanese said.

"The ideology that has been around for more than a decade that led to this ideology of hate, and in this case, a preparedness to engage in mass murder."

Albanese said Naveed Akram, 24, had come to the attention of Australia's intelligence agency in 2019 -- but he was not considered an imminent threat at the time.

"He was drawn to their attention because of his association with others.

"Two of the people he was associated with were charged and went to jail, but he was not seen at that time to be a person of interest."

Carrying long-barrelled guns, they peppered the beach with bullets for 10 minutes before police shot and killed 50-year-old father Sajid.

Naveed was arrested and is now in a coma in hospital with serious injuries, under police guard.