Shane Watson's dazzling performances with bat and ball helped Australia maintain their unbeaten record in the World Twenty20 as George Bailey's men thrashed South Africa by eight wickets in their Super Eights clash.

Watson was named man of the match for the fourth consecutive game on Sunday as Australia made 2-147 with 14 deliveries remaining in reply to South Africa's 5-146.

Watson is the leading runscorer and wicket-taker in the tournament, although India were set to play Pakistan in the second match of Sunday night's double-header at Colombo's Premadasa Stadium.

Opener Watson scored a stylish 70 off 47 deliveries after taking 2-29 with the ball.

Australia's victory is likely to be enough to send Bailey's side into the semi-finals on October 4-5.

Australia have a third and final Super Eights clash with Pakistan on Tuesday night.

After the early loss of David Warner (five), Watson added 99 for the second wicket with Mike Hussey.

Hussey was unbeaten on 45 with Cameron White on 21.

Earlier, Xavier Doherty claimed a career-best 3-20 after being recalled for his first game of the tournament. The left-arm spinner replaced medium-pacer Dan Christian in Australia's side.

Doherty opened the bowling and removed Richard Levi (0), Jacques Kallis (six) and JP Duminy (30) while Watson chipped in with the wickets of Hashim Amla (17) and AB De Villiers (21).

However the Proteas recovered from 5-86 but recovered thanks to a 60-run stand between Farhaan Behardien (31 not out) and Robin Peterson (32 not out off 19 balls).

A win to Pakistan over India in the second game on Sunday night's schedule would knock South Africa out of the tournament.