Resuming on 267 for six, overnight batsmen Clarke (138) and Mitchell Johnson (64) stitched together an invaluable 142-run stand for the seventh wicket before Nathan Hauritz (41) and Peter Siddle (23) also chipped in as Australia raised 445 runs in their first essay.

In reply, South Africa lost Neil McKenzie (23) to Peter Siddle and Graeme Smith (30 retired hurt) to injury before reaching 125 for one at stumps. They still trail the hosts by 320 runs in the first innings with nine wickets in hand.

In-form Hashim Amla (30) and veteran Jacques Kallis (36) were in the middle, having put on 49-run stand and looking good for more.

Smith hurt his little finger after a Johnson delivery bounced sharply to hit him and the South African skipper, already nursing an elbow injury, headed to the hospital for an X-ray.

Earlier, Dale Steyn and Paul Harris claimed three wickets apiece but overall, it was quite a toil for the South African bowlers who just could not get the better of the Australian tail-enders' determination.

Clarke's 10th Test century was a product of his more than six-hour vigil, during which he faced 250 balls, hitting 17 boundaries in the process.

Johnson's career best 64 came in nearly three hours, off 124 balls with 11 boundaries in it.

Neither Clarke nor Johnson, however, can claim their knock to be flawless. Clarke was dropped twice on Saturday and Johnson benefitted when Kallis grassed one at the slip this morning after the batsman had added just one run to his overnight score of 17.

Clarke, who looked shaky yesterday, was in a positive mood this morning as his confident footwork suggested. He drove and flicked with aplomb and negotiated Paul Harris without any apparent trouble.

A sharp single brought up Clarke's first century at his home ground. It was only when JP Duminy made his Test debut as an off-spinner that the batsman looked in trouble.

Eventually, it was a Duminy full toss which Clarke, trying to drive it down the ground, spooned to the bowler who dived to his left to take a sharp catch.

Two runs later, Johnson fell to Steyn when Smith took the catch in the slip, not before completing his second Test half-century.

Hauritz and Siddle also decided to make a mark with the bat and the duo added 59 runs for the ninth wicket before Harris broke the stand.

The Protea spinner first trapped Siddle and in his next over removed Hauritz after the latter had played a 48-ball cameo of 41.

When Smith and McKenzie walked out to spearhead South Africa's reply, none looked in comfort, especially against debutant Doug Bollinger.

Smith twice edged and on both occasions heaved a sigh of relief as the ball didn't carry to the slips.