Brisbane - The Wallabies kept the Tri-Nations series alive with an inspired 21-6 surprise victory over the world champion Springboks here on Saturday.

Australia laid siege to the South Africans for the entire second half to open the door for the All Blacks to come from behind to pip the Springboks with two games left in the southern hemisphere championship.

South Africa, going into the Brisbane Test leading by nine points, now face a potential make-or-break showdown with the All Blacks in Hamilton next Saturday.

The Springboks have not beaten the Wallabies in Brisbane since 1971 and have now lost all their six matches at Lang Park -- and have been held try-less in their past four Tests at the venue.

The Wallabies scored two second-half tries from centre Adam Ashley-Cooper and teenage fullback James O'Connor with Matt Giteau landing a conversion, two penalties and a drop goal.

South Africa's points came from a penalty goal and a drop goal from flyhalf Morne Steyn.

It was exactly what the Wallabies deserved as they dominated all the second-half after leading 9-6 at half-time to clinch their first win of this year's Tri-Nations series after losing their opening four games.

The Wallabies were a far different proposition to the one that were comprehensively outplayed by the Springboks in Perth last weekend.

Playing with passion and verve, the Australians ripped into the rucks and tackles with relish and led 6-0 after two early Giteau penalties.

The home side appeared to have scored in the 16th minute when rookie scrumhalf Will Genia sent winger Lachie Turner on his way to the right corner, only for Bryan Habana to tackle him into the corner post.

The South Africans had a great chance when centres Jean de Villiers and Jaque Fourie opened up the Australian midfield, but the Wallabies did well to scramble the ball clear close to the try-line.

Steyn reduced the deficit with a 29th-minute drop goal and the Australians lost two players, Turner (shoulder) and hooker Tatafu Polota-Nau (ribs) with injuries before half-time.

The Australian scrum lifted up the Springbok front row before Giteau landed a 35th-minute drop goal for the home side to lead 9-3.

Steyn landed a penalty nearing half-time but the visitors had a try disallowed when Fourie du Preez's pass was ruled forward to flanker Heinrich Brussow.

The Wallabies' intensity forced the Springboks in the second period to revert to their kicking game to find a way through the tiger-like home defence.

Genia had a try disallowed by the video referee in the 53rd minute after taking a quick tap penalty but the Springboks survived the onslaught with some determined goal-line defence.

The Springboks had another close shave when Giteau intercepted replacement winger Adrian Jacobs' hurled pass to avoid going into touch only for Fourie's tackle to prevent Giteau from getting the video referee's decision.

But the breakthrough finally came in the 63rd minute when Berrick Barnes put Adam Ashley-Cooper into a hole and the centre stormed over untouched to give the Wallabies a 10-point lead.

O'Connor, 19, clinched the match for the Wallabies when he streaked away to score four minutes from full-time, scooping up Du Preez's dropped ball.