Champions Australia started their World Cup defence on a positive note by crushing Zimbabwe to record a 91-run victory in their opening World Cup match on Monday.

Chasing 263 for victory, the Zimbabweans could only muster 171 in reply.

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Earlier, tangled by a barrage of inspired spin bowling, Australia looked guarded in their approach at the start and needed some powerful hitting at the end in front of a quarter full stadium in Ahmedabad on a surface which had no demons in it.

Lusty hitting by vice-captain Michael Clarke (58 not out off 55 balls), David Hussey and Steve Smith at the close of the innings ensured Australia went past the 250-run mark.

The fourth-wicket stand between Clarke and White yielded 63 runs off 73 balls.

Zimbabwe started with paceman Chris Mpofu and the experienced left-arm spinner Ray Price at the other end, and both bowlers managed to keep openers Shane Watson (79) and Brad Haddin under check as they managed a meagre 28 runs in the first 10 overs.

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Haddin, on 16, was lucky to survive when the ball trickled on to the stumps after hitting his pad, but failed to dislodge the bails.

What was surprising was the approach from the openers who never looked to attack the bowlers, barring the 14th over from Mpofu which went for 17 runs and included four boundaries.

Watson, continuing his good form that enabled him to score over 800 runs in the 2010-11 season, started on a cautious note before opening up to score a well-crafted 79 off 92 balls, after Ricky Ponting opted to bat first at the Sardar Patel Stadium.

The sweep shot, a preferred choice of batsmen against slow bowling was not employed much, as the Zimbabwe spinners went through their overs at breathtaking pace.

At one point their over rate was 17 overs per hour, three more than the desired rate.

The Zimbabweans also used the Decision Review System judiciously and were successful on both their referrals to get rid of Watson and Haddin leg before to their spinners.

On both occasions it was former captain and wicketkeeper Tatenda Taibu who made sure that the decisions went upstairs to the third umpire.

After building a 61-run stand with fellow-opener Brad Haddin (29), Watson came to the fore once again when he joined by Ponting in the middle. Watson was also involved in another half-century stand with Ponting (28), both batsmen completing a 79-run (75 balls) partnership.

Ponting and Watson managed to up the scoring rate but Watson's dismissal and subsequently Ponting's run out hampered their tempo once again.

Captain Ponting was run out at the non-striking end by a brilliant direct throw from the mid-wicket boundary by the lanky Mpofu while attempting a second run.

Chasing a formidable 263 for victory, the Zimbaweans failed to counter the Australian bowlers.

Australia's speedsters Brett Lee, Shaun Tait and Mitchell Johnson (four for 19) regularly hit the 145 kph mark to reduce Zimbabwe to 44 for four within 13 overs, from which the African nation never recovered and they were all out for 171.

While Lee and Tait resorted to the short pitch stuff, Johnson kept it full and fast to torment the Zimbabwean batsmen.

Off-spinner Jason Krejza also chipped in with two wickets after the pace battery had done its job with the new ball -- giving Australia their 30th consecutive win in the 50-over tournament.

Zimbabwe only managed to delay the inevitable with a 44-run fifth wicket partnership and an eighth-wicket stand of 49 runs, between Prosper Utseya and Graeme Cremer, as the result was well decided within the first 15 overs.