Symonds celebrates the wicket of Jacques Rudolph

Australia look set to wrap up victory on Friday after reducing South Africa to 99-6 at stumps on the penultimate day of the second Test at the MCG.

The hosts had declared on 321-7, with South Africa chasing 366 to win.

Matthew Hayden struck his 25th Test century in a fluent stand of 124 with Andrew Symonds, who hit six mammoth sixes and five fours in a Test best 72.

Symonds then took two wickets and Shane Warne three as the visitors lost six wickets for 43 runs in 18 overs.

The hosts began the day on 110-2 and despite the loss of Brad Hodge, who was caught behind off Andre Nel for 24 when replays suggested that there was no contact, they dominated the morning session.

We are pretty down about it... it has been a titanic struggle Mickey Arthur SA coach Reaction: Day four quotes

Mike Hussey, who scored 122 in the first innings, was well caught low at slip for 31 after Graeme Smith turned one sharply out of the rough.

But Symonds atoned for his golden duck on day one by hitting left-arm spinner Nicky Boje for six off the first ball he faced.

The last three wickets finally fell to Jacques Kallis in the space of four balls before the declaration was made.

Having completed his fourth Boxing Day Test century in five years, Hayden finally went when he edged a pull to wicket-keeper Mark Boucher.

Hayden has scored four centuries in his last five Boxing Day Tests

Symonds was well caught by Nel on the mid-wicket boundary before Adam Gilchrist's poor run continued when he ambitiously pulled his opening delivery and skied a catch to Ashwell Prince in the deep.

Skipper Smith and AB de Villiers managed to see out eight overs until the break before the collapse began.

De Villiers was drawn out of his crease by spin wizard Warne, giving Gilchrist a simple stumping.

And the keeper safely pouched Smith when the touring skipper chased an away swinger from Glenn McGrath.

More magic from Warne accounted for Herschelle Gibbs, who was flummoxed by a quicker delivery that came back in at him.

With only four wickets remaining the writing is on the wall From BB Have your say on TMS

Symonds continued his impressive display by finding the edge of Kallis with one that held its line and forcing Jacques Rudolph to play onto his stumps.

Prince and Boucher briefly defied Australia, and Warne, Gilchrist and skipper Ricky Ponting all had discussions with umpire Asad Rauf over persistent padding away by the batsmen.

They thought they had been denied again after Boucher edged into his pad off the back foot and Ponting took an athletic catch to his left at silly point.

Rauf merely directed the fielders to the batsmen, however, who was making his way back to the pavilion.

Had Australia captured a seventh wicket, it is likely they would have requested the extra half hour available if victory is within realistic sight.

Prince had a reprieve on 13 when he was beaten by a turning one from MacGill that passed his pads down the leg-side, but Gilchrist fumbled and eventually took the bails off when not fully in control of the ball.

After the first referral of the match to the third umpire, the dogged left-hander was eventually given the benefit of the doubt.

Shaun Pollock was also fortunate to survive, having been expertly caught low at silly point by the ever-alert Ponting, only for Warne to over-step.

South Africa have been further hampered by a knee injury to paceman Makhaya Ntini, who is expected to miss next week's third and final Test in Sydney.