DURBAN, South Africa (AP):

Australian opening batsman Phillip Hughes' contrasting centuries against South Africa in the second Test represented a special moment in his fledgling international career.

The 20-year-old Hughes hit 136 not out as Australia reached 292-3 after the third day, to extend their lead to 506 runs.

Aggressive first innings

He had scored a more aggressive 115 in the first innings for his maiden Test century, breaking the record of former West Indian batsman George Headley as the youngest player to hit two hundreds in one match - and in just his second Test.

"It's something I'll never forget, a very special moment," Hughes said.

Hughes' first-innings total came off 151 balls, while his second required 301 deliveries.

"Every day is different and today I had to grind it out, tough it out. I was determined not to give it away after I got a start," he said.

South Africa will have to stage a remarkable comeback if they are to save the match and stay in the three-Test series. Australia lead 1-0.

J.P. Duminy finished on 73 not out after watching from the non-striker's end as his last two partners, Dale Steyn and Makhaya Ntini, were dismissed in the first three balls of the day.

Duminy said the hosts would draw inspiration from former stalwart Gary Kirsten's heroic 275 to save a Test against England at Kingsmead in December 1999.

Positive attitude

"If we come out with a positive attitude, who knows what might happen," Duminy said.

"We have the character to come back with a good performance Monday."

South Africa are unlikely to have the services of opener and captain Graeme Smith, who fractured his little finger when hit by fast bowler Mitchell Johnson on Saturday.