Published: Jan 07, 2012 6:19 PM EST
Updated: Jan 08, 2012 7:31 AM EST

EAST LONDON, South Africa (AP) - Defending champion Louis Oosthuizen birdied three of his last four holes for a 6-under 67 Saturday to share the third-round lead at the Africa Open.

Oosthuizen and Tjaart van der Walt (65) were tied at 21-under overall, one shot ahead of 2009 winner and two-time U.S. Open champion Retief Goosen (66).

Van der Walt birdied the first four holes at East London Golf Club and had nine in his round, offset by one bogey.

Van der Walt, who turned professional in 1996, has yet to win a tournament.

Goosen, shooting into a wind on his approach to 18, landed in a greenside bunker to finish with par. Oosthuizen and Van der Walt each made birdies to take the lead.