The men in gold eventually ran in six tries to two over their Pacific neighbours but they were made to work by the Fijians who took a two-point advantage into half-time and extended their lead with an early second half try.

Fiji came out in predictably physical fashion, mixing in big hits in defense with some powerful carries and flair in attack to open up a 21-12 lead after 45 minutes.

But as the second half wore on, Michael Cheika's men found their spark and turned around a mistake-ridden start to pile on the points and run away with an important bonus-point win.

The Australians scored two first half tries, the first by skipper Michael Hooper who barged through would-be tacklers for his, before Reece Hodge finished neatly in the corner of some slick hands for Australia's second.

But those tries weren't good enough to give the Wallabies the lead at the break, with Fijian standout Peceli Yato registering the first five-pointer inside 8 minutes of play and Ben Volavola landing three penalty goals to send Australia to the dressing rooms down 12-14.

It wasn't until midway through the second stanza that the Wallabies pack took control of the match, with hooker Tolu Latu's powerful effort off a maul in the 57th minute opening the floodgates.

Latu notched another one from a lineout drive five minutes later, after Fiji centre Levani Botia was yellow-carded, and the Wallabies continued to heap the set-piece pressure on a tiring Fijian pack.

The backs would also eventually get in on the action with Fijian-born duo Samu Kerevi and Marika Koroibete crossing late to finish the job and give the Wallabies the result they were looking for to kick off their Rugby World Cup 2019 campaign.

Koroibete said playing in the world cup was a dream come true but admitted to some emotions facing Fiji.

He said there was a lot to be learnt from the opening game and hopefully it would create the momentum needed to succeed.

The wing was delighted that he was able to score a try, particularly as it was from a set play the team had been practising all week.

"To get the try from the set-piece was a pretty special one," Koroibete said.

Wallabies lock Izack Rodda said the Fijians stared the game at break-neck speed and piled the pressure on the Australians.

"They came out of the gates flat-out, got ahead of us and their physicality was pretty good." Rodda said.

"After half-time we started to fall into our own game plan and sticking to our processes.and started to get some pay with the driving maul."

Wallabies 39 (Tolu Latu 2, Michael Hooper, Reece Hodge, Samu Kerevi, Marika Koroibete tries; Matt To'omua 2, Christian Lealiifano cons; Reece Hodge pen) defeated Fiji 21 (Peceli Yato, Waisea Nayacalevu tries; Ben Volavola con; Ben Volavola 3 pens)