Aiden Markram survived two dropped catches and went on to make 84 as South Africa extended their lead beyond 200 in the third Test against Australia on Saturday.

Markram was out for 84 shortly before tea on the third day, which South Africa reached on 151 for three, an overall lead of 207, at Newlands.

Markram, out for nought in the first innings, could have completed a "pair" but he was dropped off the fourth ball of the second innings when he edged Mitchell Starc low to the left of Usman Khawaja at gully.

He survived another much more difficult chance on 59 when Australian captain Steve Smith flung himself to his right at second slip and got his fingertips to a flying edge off Josh Hazlewood.

Smith, who held a world record-equalling five catches in the first innings, had already added to his tally by catching first innings century-maker Dean Elgar off Pat Cummins for 14.

Markram, who made a century in the first Test in Durban, batted solidly despite his lapses and hit ten fours and two sixes in a 145-ball innings. He shared partnerships of 76 with Hashim Amla (31) and 47 with AB de Villiers, who was unbeaten on 18.

Markram was out in the last over before tea when he chipped Mitchell Starc to mid-on where Cummins held a low catch.

The series is poised at one match apiece.

De Villiers opened his scoring with a slapped six off the back foot over cover off Cummins but it was the only scoring shot in the first 20 balls he faced as he made a cautious start to his innings.

There was a moment of potential drama when the umpires questioned fielder Cameron Bancroft over what appeared to be an object in his pocket when he had the ball in his possession.

But play continued without the ball being changed and it was unclear what was discussed.