Dean Elgar digs in as South Africa build commanding lead over Australia

South Africa 488 & 134-3, Australia 221: Elgar will resume on the fourth morning, with Faf du Plessis, as the pair look to increase the lead towards the 500-run mark

Dean Elgar dug in as South Africa built a commanding lead over Australia (AFP)

South Africa opener Dean Elgar dropped anchor to steer his side to 134 for three in their second innings at the close of the third day of the fourth and final test against Australia on Sunday, giving the hosts a daunting lead of 401 runs.

Elgar amassed 39 from 158 balls in a patient knock that has been the glue for South Africa's second innings, as they look to build an unassailable lead with two full days remaining at the Wanderers.

Australia need victory to avoid a first series defeat in South Africa since 1970, but have been rocked by the ball-tampering scandal that saw former captain Steve Smith, his deputy David Warner and batsman Cameron Bancroft sent home and slapped with hefty bans after the third test in Cape Town.

Elgar will resume on the fourth morning, with his captain Faf du Plessis on 34, as the pair look to increase the lead towards the 500-run mark.

Paine dug in as Australia posted 221 (Getty)

With so much time left in the test, a declaration at that point would make South Africa heavy favourites to win or secure a draw at the very least.

The wicket is beginning to misbehave with variable bounce and there is sideways movement to assist the bowlers, which has brought Australia some success.

The excellent Pat Cummins (2-35) removed in-form Aiden Markram (37) when he edged to Peter Handscomb at second slip, but not before the opener, playing just his 18th test innings, went past 1,000 runs in the five day game, the second fastest to reach that mark for South Africa behind Graeme Smith (17 innings).

Hashim Amla (16) was caught at backward short leg by Mitchell March from a Nathan Lyon delivery, while AB de Villiers (six) gloved a rising Cummins ball to wicketkeeper Tim Paine.

Elgar led from the front as South Africa looked to put the game out of sight (Getty)

South Africa had earlier bowled Australia out for 221 in their first innings with a rush of wickets after lunch having been frustrated in the morning session by Paine (62) and Cummins (50), who put on 99 for the seventh wicket.

New Australia captain Paine batted bravely with a stress fracture on his thumb to score a valuable half-century, his fourth in test cricket, but was the last man out as Elgar took a brilliant running catch at mid-off from a Kagiso Rabada (3-53) delivery.

Cummins was the only wicket to fall in the morning session when he was trapped leg before wicket by spinner Keshav Maharaj (3-92), but South Africa ran through the tail after lunch.

The home side have a fitness worry as seamer Morne Morkel, playing in his final test before retirement from international cricket, was forced from the field with a left side strain, but he did return to the pitch after the interval and will be monitored overnight.