Shane Watson continued his impressive form with both bat and ball as Australia cruised to a comprehensive eight-wicket victory against South Africa in their Super Eight match in the World Twenty20 on Sunday.

Watson picked up two wickets for 29 with the ball and then cracked 70 off just 47 balls for his fourth consecutive man-of-the-match award in as many matches in the tournament.

Chasing 147 for victory, Australia lost opener David Warner early but Watson snubbed South Africa's hopes of victory with a 99-run stand for the second wicket with left-hander Mike Hussey (45 not out).

The all-rounder, who is now both the highest scorer and wicket-taker in the tournament, hit eight boundaries and two massive sixes du ring his knock before he was out caught by Wayne Parnell off left-arm spinner Robin Peterson.

"It's nice to be able to continue to play well. I know how important my role is. There's still a hell of a long way to go," Watson said during the post-match presentation ceremony.

"Facing Dale Steyn and Morne Morkel was always going to be a big challenge. I knew we have to get through it without getting out, scoring as many runs as we can.

"The top four batsmen are the ones who win you games consistently. (Mike) Hussey took the pressure off me to score."

Peterson was unlucky when Parnell dropped a difficult catch off his bowling to dismiss Watson when he was on 52. Captain and wicketkeeper AB de Villiers also missed a stumping chance to dismiss Hussey off the same bowler.

Australia's left - arm spinner Xavier Doherty , playing his first match of the tournament, picked up three wickets for 20 to put South Africa on the backfoot after Australia ha d op ted to field first.

Doherty dismissed opener Richard Levi and Jacques Kallis in his first two overs and later took the wicket of Jean-Paul Duminy (30) as South Africa struggled for momentum.

Peterson (32 not out) and Farhaan Behardien (31 not out) added 60 runs for the unbroken sixth wicket to help their team r e ach 14 6 for five.

South Africa captain de Villiers said his side needed early wickets, especially that of Watson to defend the total.

"You got to get wickets if you want to win Twenty20 games like they (Australia) did early on. They got wickets and put pressure on a regular basis, but we couldn't do that," de Villiers told reporters.

"If you don't get Watson early on, he is going to take away the game, that's what exactly happened.

"It was really hard to control the game against him and when Hussey came in, it was two different players, right and left hand combination, it was quite tough.

"We have played really good cricket in these conditions in the past. So it is very disappointing. They (Australia) adapted to the situation better than us."

Australia have now won both their Super Eight games while South Africa are on the brink of elimination having lost both their matches.