Jamie Heaslip of Ireland celebrates victory over one of the tournament favourites Australia [GALLO/GETTY] 

Ireland produced the first major upset of the World Cup with a 15-6 victory in a heavyweight thriller of an encounter played in a febrile atmosphere at Eden Park on Saturday.

Coming into the match on the back of four warm-up defeats and a shaky opening victory against the U.S., the Irish tackled and harried and hustled their way to a first victory over Australia in five attempts at World Cups.

Two penalties and a drop goal from Jonathan Sexton and another two penalties from Ronan O'Gara won the match but it was the sweat of the Irish pack which earned the plaudits that were showered down on the players from the green-clad majority in the 58,678 crowd.

"We swear we were in Dublin," Irish skipper Brian O'Driscoll told reporters.

"We swear we were in Dublin"

Irish captain Brian O'Driscoll

"Absolutely incredible support and it was our job to give them something to shout about and thankfully we did.

"We were mentally in a place where we owed ourselves a big performance."

Tri-Nations champions Australia were robbed of injured flanker David Pocock and sick hooker Stephen Moore earlier on Saturday but their much-vaunted backline never really got going on a wet pitch, which also more resembled Dublin than Sydney.

Barring a huge upset in their remaining games, Ireland will now top Pool C and go through to a quarter-final against the second-placed team from Pool D, which is likely to be Wales, Fiji or Samoa.

"It's just half the job done," O'Driscoll added.

"We have two wins and two more to get so, as much as we'll enjoy this, let's not lose sight there are two more games."

Early clash of titans

Australia must now be resigned to finishing second and a likely last eight match-up against defending champions South Africa with, if they get through that, the All Blacks prospectively waiting in the semi-finals.

"The Irish did well to spoil our ball, we couldn't get any momentum and we played some dumb footy," Wallabies skipper James Horwill said.

In an often abrasive first half, Australia looked the brighter in attack with full back Kurtley Beale particularly
incisive, but the Irish had great success in holding up the Wallaby runners and winning put-ins to the scrum.

Two penalties from James O'Connor and a penalty and drop goal from Sexton left the sides deadlocked at 6-6 going into halftime, the same score as Australia had shared with Italy halfway through their opening match.

Sexton added a second penalty to put Ireland 9-6 ahead after 50 minutes and saw another ping off the post two minutes later.

          Australia look dejected after a surprise early defeat in their World Cup campaign [GALLO/GETTY] 

Quade Cooper and Beale kept trying to kickstart their usually potent offence, but the green defenders would bend a little before swallowing the Wallabies backs up and winning more scrum put-ins with their aggression at the breakdown.

Ronan O'Gara, on for centre Gordon D'Arcy, put the Irish a further three points ahead after a fourth penalty was awarded against the Australians for infringements at the scrum after 61 minutes.

A Will Genia charge towards the Irish line was brought back for crossing before a huge Sexton up-and-under led to another scrum under the Australian posts and another penalty against the Wallabies front row.

As the rain started to fall on Eden Park again, O'Gara slotted the three points to stretch the lead to nine.

The Australians camped on the Irish line but neither forward nor back could break through the green wall and Tommy Bowe finally broke the siege with an interception from a Cooper offload.

The Irish winger's charge the length of the pitch was ended short of the line by an O'Connor tackle but Australian hopes of a comeback to match that of the 1991 Wallabies in Dublin had now gone.

In the earlier matches, South Africa took Fiji apart in a clinical performance, running in six tries to earn a 49-3 victory in their Pool D match at the Wellington Regional Stadium.

"Fiji dominated the first 20 minutes and we missed five or six tackles that gave them momentum in the game," Springboks coach Peter de Villiers told reporters.

"We can't allow that going forward. We pride ourselves on our defence and it worked pretty well in our favour but we must be ruthless on defence."

Argentina roared back into the World Cup mix with a superb six-try, 43-8 destruction of Romania in a one-sided Pool B clash, setting up a mouth-watering meeting with Scotland for a probable quarter-final berth.

Source: Agencies