SYDNEY (AFP) - Australia's Cate Campbell broke the 100 metres freestyle world record on Saturday at a meet in Brisbane, as she prepares for the Rio Olympics.

"We present your new new world record holder in the 100 free," tweeted the Australian Swim Team, confirming the 52.06sec swim which eclipsed German Britta Steffen's old mark of 52.07 set way back in the full-body supersuit era in 2009.

Campbell, 24, had "put the world on notice" at the Brisbane Grand Prix, it added, with Australian swim great Dawn Fraser at poolside to witness the new record.

She had already notched an impressive win over her sister younger Bronte, the reigning world 100m free champion, in the 50m free on Friday.

"I still can't believe it's happened," she told reporters after her win. "People have been asking me when I was going to break the world record for the last three years and honestly it wasn't really on my mind but every time I got in the pool, it was like will they stop asking me this question now. Now you will."

In April, Cate had edged out her sister to win an epic 100m free final at the Australian Championships and Olympic trials in Adelaide. The Campbell sisters headline a 34-strong Australian swim team heading to Rio, with several ranked world No. 1 on current form.

A strong showing in Brazil would be a major turnaround for the squad, which produced just one gold at the 2012 London Olympics in a campaign marred by ill discipline, drug use and drunkenness.