Louis Oosthuizen will take a three-shot lead into the final round of the ISPS HANDA Perth International after taking advantage of good scoring conditions on Saturday.

The South African fired a brilliant 64 on Friday, and said following that round that he thought another low one was possible at Lake Kurrinyup Country Club.

He was on course for a potential repeat as he briefly opened up a five-shot advantage on the back nine but two late bogeys - after going 40 holes without a dropped shot - saw him sign for a 67 and left the door ajar for the chasing pack.

That will be led by American Peter Uihlein and France's Romain Wattel, who are both 12 under and a shot clear of Australian Jason Scrivener.

World Number 21 Oosthuizen is seeking his first European Tour win in two years after a winless 2015 broke a run of five consecutive seasons with a victory.

Oosthuizen birdied the first and third while Uihlein opened birdie-bogey-birdie to surrender his overnight advantage.

Oosthuizen then rolled in a 30-foot putt for birdie on the sixth and nestled his eagle putt on the seventh right up to the hole to open up a two-shot lead.

That would not last for long, though, as Uihlein got up-and-down from the back of the green to birdie the seventh and then put his tee shot on the eighth inside four feet for another gain.

Another brilliant approach to the ninth made it three birdies in four holes for the 2010 Open Championship winner and after a poor tee-shot on the 12th, Uihlein needed three attempts to find the green and signed for a triple-bogey.

Oosthuizen made a remarkable up-and down from the back of the 14th green and followed it with another birdie to get to 17 under, but Uihlein also took advantage of that gettable duo and when a poor putt on the 16th coupled with a misjudged tee-shot on the next saw Oosthuizen go bogey-bogey, the lead was back down to two.

A bogey on the last then saw Uihlein sign for a 71 and join Wattel at 12 under.

Wattel recorded a flawless 65 with the help of a run of four birdies from the second, while Scrivener had an eagle on the 14th and two birdies but dropped his only shot of the day on the last.

Perth native Brett Rumford had been four over for the day after 13 holes but went eagle-eagle with the help of a brilliantly holed bunker shot on the 14th and goes into the weekend ten under, a shot clear of Marcus Fraser, Mikko Korhonen, Richard T Lee, Alexander Levy and Mardan Mamat.