BRISBANE (AFP) - Under-fire Australia coach Ewen McKenzie has quit, officials said on Saturday in a shock announcement after the narrow 28-29 loss to New Zealand.

The resignation, ahead of next year's World Cup, follows rumours of discontent in the Wallabies camp and comes after McKenzie was forced to deny an extra-marital affair with a staff member.

Malakai Fekitoa's converted try in the dying seconds denied Australia as the All Blacks snatched a breathtaking 29-28 victory in the dead-rubber Bledisloe Cup tie.

Australia had looked certain to take a famous win when they led 28-22 with time all but up, but the world champions dashed their hopes when Fekitoa crossed with just three seconds left.

Replacement fly-half Colin Slade then coolly slotted the conversion from 15 metres from the sideline to end a brave challenge from an under-seige Australian outfit.

Australia, who have not beaten New Zealand since 2011, were in turmoil heading into the Test after back Kurtley Beale was suspended following a series of off-field incidents.

There had also been increasing questions over McKenzie after successive losses to South Africa and Argentina in the Rugby Championship and rumours of discontent.

However, there were no signs of disharmony as the Australians played with more passion than at almost any time throughout the season.

The hosts survived an early onslaught from the All Blacks and then gradually began to get the better of their opponents as the match wore on. They took a 15-12 lead into half-time and extended that to 22-12 and then 25-15 before the All Blacks, who were down to 14 men, struck back to make it 25-22 with 10 minutes remaining.

Another Australian penalty made it 28-22 before New Zealand engineered their great escape, to the dismay of most of the 43,000 fans at Brisbane's Suncorp Stadium.

New Zealand had all the running in the opening 10 minutes but it was the Australians who struck first when scrum-half Nick Phipps darted over to open the scoring.

However, the All Blacks hit straight back, reclaiming the ball from the kick-off and feeding winner Cory Jane, who dived over in the corner. Wallabies fly-half Bernard Foley kicked a penalty to make it 10-7, but the lead lasted only three minutes as New Zealand hooker Dane Coles crossed after throwing a spectacular dummy 15 metres out and beating three defenders to the line.

However, the Wallabies hit the front once more when Foley dived over in the corner from the base of a ruck.

The Wallabies were first to strike in the second half as their big ball runners began to make some easy ground. Wallaby winger Adam Ashley-Cooper, playing his 100th Test, crossed in the corner and when Foley kicked the conversion, Australia led 22-12 four minutes into the second half.

A Beauden Barrett penalty 13 minutes into the half brought the score back to 22-15, but Foley replied soon after to restore the 10-point advantage. All Blacks scrum-half Aaron Smith darted over to close the gap once more, before Fekitoa's heroics sealed victory.