Australia opened their World Cup campaign with a 28-13 victory over Fiji in Cardiff but their failure to pick up a bonus point could prove decisive in the final reckoning.

Pool A rivals England and Wales will have been delighted by Fiji's stern second-half resistance as Australia, 25-3 ahead three minutes into the second half, failed to prosper from a position of strength.

England claimed a bonus point against Fiji in their tournament opener at Twickenham, albeit in the final seconds, and Australia must improve when they meet the real heavyweights of this section.

Fiji are almost certainly the first team to perish in the so-called Pool of Death after their opening two games, but the South Sea Islanders can hold their heads high after outplaying Australia in the second half only five days after their Twickenham showing.

There was huge support for Fiji among a 67,000-plus crowd at the Millennium Stadium and Ben Volavola's second-half try was greeted with the sort of roar normally reserved for Wales tries in Cardiff.

But David Pocock's brace in the space of four first-half minutes and Sekope Kepu's try just after the break ensured Australia would get off to a winning start.

Australia chose to play a dynamic game with their two openside stars, Pocock and Michael Hooper, in the back row and they hit the ground running as Fiji were forced to retreat.

Fiji were without back-row forward Dominiko Waqaniburotu, suspended after being cited for a dangerous tackle on England's Jonny May, and they lost wing Waisea Nayacalevu to injury within minutes of the first whistle.

Australia's approach was to get the ball whenever they could and in Israel Folau they had a full-back willing to enter the line at all times and determined to cause danger.

Pressure brought points when Foley landed a 10th-minute penalty but Fiji were level after they had entered the Wallabies' 22 for almost the first time midway through the half.

The South Sea Islanders turned down an initial kick at goal and almost cashed in from Volavola's kick into the corner, Folau climbing well to prevent replacement Asaeli Tikoirotuma from scoring.

But Fiji could not turn down points the second time after Australia had infringed and Nemani Nadolo stroked over a penalty in front of the posts.

Nadolo escaped a yellow card for a high tackle on Folau but Fiji were not so fortunate when Pocock profited from some driving Wallabies' play and Foley converted for a 10-3 lead.

Fiji's problems grew when prop Campese Ma'afu was yellow-carded for kicking the ball away at the base of a ruck and their one-man disadvantage told as they failed to stop Australia's powerful rolling maul.

Pocock was again the man driving the pack and crashed over for his second try, and although Foley missed the conversion, the outside-half was soon on target from 30 metres to give Australia an 18-3 interval lead.

With points difference possibly vital at the end of the group, Australia knew this was an opportunity to put their foot to the floor and Kapu crashed over within three minutes of the re-start after hooker Telemaitoga Tuapati had fallen off a tackle.

But Nadolo responded with a penalty and Fiji found a second wind where they reverted to type and began to stretch the Wallabies' defence with their running ability.

And Volavola picked a lovely gap between Australia second-row forwards Rob Simmons and Kane Douglas on the hour to glide under the posts for a try which Nadolo converted.

Fiji might have been expected to tire after their Twickenham exertions and Australia were content to extend their lead to 28-13 through Foley's third successful penalty rather than chase the bonus-point try.

Australia lost centre Tevita Kuridrani to a yellow card inside the final 10 minutes to virtually end their hopes of picking up a bonus point.