Australia will use a sweeping buyback scheme to "get guns off our streets", Prime Minister Anthony Albanese said on Friday as hundreds plunged into the ocean to honour Bondi Beach shooting victims.

Sajid Akram and his son Naveed are accused of opening fire on a Jewish festival at the famed surf beach on Sunday, killing 15 people in one of Australia's deadliest mass shootings.

Albanese vowed to toughen laws that allowed 50-year-old Sajid to own six high-powered rifles.

"There is no reason someone living in the suburbs of Sydney needed this many guns," he said.

Australia would pay gun owners to surrender "surplus, newly banned and illegal firearms".

It would be the largest gun buyback since 1996, when Australia cracked down on firearms in the wake of a shooting that killed 35 people at Port Arthur.

Australia will remember those slain at Bondi with a national day of reflection, the prime minister said.

Albanese urged Australians to light candles at 6.47pm on Sunday, December 21 – "exactly one week since the attack unfolded".

Many hundreds returned to the ocean off Bondi Beach on Friday in another gesture to honour the dead.

Swimmers and surfers paddled into a circle as they bobbed in the gentle morning swell, splashing water and roaring with emotion.

The Bondi beach gesture came as a married couple who were shot and killed as they tried to stop the gunmen were laid to rest at a Jewish funeral home.

Bondi locals Boris and Sofia Gurman were among the first killed as they tried to wrestle 50-year-old Sajid to the ground.

"The final moments of their lives they faced with courage, selflessness and love," rabbi Yehoram Ulman told mourners. "They were, in every sense of the word, heroes."

Sydney remains on high alert almost a week on from the shootings.

Armed police arrested seven men on Thursday evening after receiving a tip they may be plotting a "violent act" at Bondi Beach. (AFP)