(CNN) -- Defending champion Louis Oosthuizen raced to the halfway lead at the Africa Open with a superb 11-under-par 62 at East London Golf Club Friday.
It was just one shot outside Richard Sterne's course record and left the 2010 British Open winner on 15-under 131 -- two clear of a four-strong chasing pack.
With compatriots Jaco Ahlers, Thomas Aiken, Retief Goosen and Tjaart Van der Walt on 13-under 133, it saw an all-South African top five at the European Tour event.
The 29-year-old Oosthuizen, who started on the 10th, completed his front nine in four-under 32.
But he reserved his best golf for the front nine, finishing with an eagle and three birdies in his final five holes to come home in just 30.
"I was aggressive on the putter. I went about six foot past a few times and I had to make those for par," Oosthuizen told official European Tour website.
"The last one I made on the eighth would have been eight or ten foot past, but it hit the middle of the cup.
"But I was aggressive because yesterday I left a few putts short and you're not going to hit it that far past on these greens."
Van der Walt's 64 included successive eagles -- a hole-in-one at the second followed by a 20-footer for a three at the par five third.
Overnight leader Aiken had to settle for a 69, while Goosen had a 68 as he seeks his first European Tour win in five years. Ahlers recorded the same score.
Swede Magnus A Carlsson was the first non-South African on 12-under after a 65.
Meanwhile in other golf news Friday, European Ryder Cup star Paul Casey is facing a lengthy layoff after dislocating his right shoulder while snowboarding in Colorado.
Casey was due to defend his Volvo Golf Champions title in South Africa in two weeks and is set to miss the Tour's lucrative Middle East swing,
"The good news is that the experts I've seen say I don't need surgery and, having already started my rehabilitation exercises, I should be back hitting balls in a few weeks," he told the Press Association.