Morkel (left) and Proteas captain Smith celebrate in Mirpur

South Africa dethroned Australia as the world's top-ranked one-day team with an emphatic victory over Bangladesh to complete a 3-0 series whitewash.

After opting to bat first for the third successive match, the hosts were again woefully out of form as Albie Morkel (4-29) helped bowl them out for 143.

Herschelle Gibbs fell early but Graeme Smith (68 no) and AB de Villiers (40) steered South Africa towards the win.

Smith hit a six to seal a seven-wicket triumph off just 34.2 overs.

The result puts South Africa ahead of Australia in the one-day international rankings by a mere 0.191 rating points but provides them with a timely boost ahead of the three-match Test series in India.

Our bowling was good but the batting left a lot to be desired - we could not cross the 200-run mark in any of the three matches Mohammad Ashraful, Bangladesh captain

And, but for a decent enough start that saw Tamim Iqbal and Shahriar Nafees put on 34 for the first wicket, the outcome was never in doubt.

And it sees Smith's side end their tour, which included two Tests, with a 100% record.

South Africa have now not lost a one-on-one ODI series - including matches against all the leading nations - since being beaten by Sri Lanka in August 2004.

But their cause was aided by a Bangladesh team which failed to capitalise on the home conditions and threw away cheap wickets through a combination of poor technique and a lack of concentration and patience.

They were unfortunate to lose Iqbal, who was sent back to the pavilion by umpire Nadir Shah despite replays showing Morkel's delivery clipped his pad rather than bat before travelling to wicketkeeper de Villiers.

Morkel shined in what was South Africa's second string attack

Nafees clearly edged Morne Morkel behind before brother Albie had Mohammad Ashraful taken by Hashim Amla at mid-on.

The talented Bangladesh captain has struggled desperately against South Africa - who rested strike bowlers Andre Nel and Charl Langeveldt - managing a paltry 17 runs in the series and he has now reached double figures in only one of his last five ODI innings'.

Mohammed Nazimuddin was caught by Smith after ridiculously attempting to slog a full-length delivery across the line and lofting it to midwicket.

Off-spinner Johan Botha, who finished with 3-34, bowled Saqibal Hasan and had Abdur Razzak caught behind, with Raqibul Hasan's run-out and Paul Harris' dismissal of Dhiman Ghosh wedged in-between.

Mashrafe Mortaza and Mosharraf Hossain both clipped to de Villiers to leave South Africa chasing well under 200 for the third time in the series.

606: DEBATE South Africa have not got where they are via the results of this series alone, it is a culmination of their fine form in recent months and years David O, BBC Sport

And despite the loss of Gibbs, who was snapped up by Ashraful in the covers off Razzak, the Proteas cruised to their target.

Petersen, cautious in the face of a turning pitch yet quick to pounce on wayward deliveries, was trapped plum by Hossain and de Villiers, whose knock came off 37 balls with seven fine boundaries, was bowled by a Farhad Reza delivery that nipped back.

By that point the imperious Smith had notched his 36th ODI half-century with a four through extra cover and it was fitting that the captain hit the winning runs by coming down the track to Saqibal and lofting him over long-on for a maximum.

"We have done it the hard way here on slightly under-prepared wickets. We have bowled, batted and fielded well.

"This has been a great preparation for the India tour."

"The series has been a learning curve for the whole team and we will try to overcome the disappointments with a better show in the future."