Phillip Hughes powered to his second century of the match as Australia [Images] extended their lead over South Africa [Images] to 506 at the close on the third day of the second Test at Kingsmead on Sunday.

• Scorecard: Australia vs South Africa, 2nd Test

Hughes advanced to 136 not out as Australia surged to 292 for three in their second innings. The opener, who hit his maiden Test ton in the first innings, became the youngest player to score a century in each innings of a Test at 20 years and 98 days old.

West Indian George Headley was the former record-holder with 114 and 112 against England [Images] in Georgetown in 1930 aged 20 years and 297 days old.

The left-handed Hughes and captain Ricky Ponting [Images] added 164 in just over three hours for the second wicket as Australia piled on the misery for the South African bowlers.

Ponting fell for 81 when he sent a pull off Morne Morkel [Images] to Neil McKenzie [Images] at deep midwicket and Michael Hussey [Images] (19) followed him back nearly an hour later when he edged a delivery from off-spinner JP Duminy [Images] that turned away from him and Jacques Kallis [Images] took smart catch at slip.

Hughes continued to stamp his dominance on the bowlers, however, going to his century in 277 minutes off 247 deliveries.

Left-arm spinner Paul Harris was the only member of a poor South African attack to stem the flow of runs, conceding just 68 runs in 31 overs.

The post-lunch session was dominated by Ponting as he notched another personal milestone in his glittering career.

Ponting became the second-highest Australian run-scorer when he reached 61 and 10,928 career runs to overtake his predecessor as captain, Steve Waugh. Alan Border is the top run-scorer with 11,174.

The visitors needed just three balls to wrap up South Africa's first innings for 138, but captain Ponting chose not to enforce the follow on.

Australia, who won the first Test by 162 runs, scored 352 in the first innings and will win the three-match series if they triumph in the second Test.