Quinton de Kock hit a brilliant 174, his third century of the World Cup, as South Africa hammered Bangladesh by 149 runs in Mumbai on Tuesday.
The Proteas were briefly in trouble at 36-2 after winning the toss but rallied strongly, taking 144 runs off the last 10 overs to finish on 382-5 amid a barrage of boundaries.
It was a total Bangladesh never looked like chasing down as they collapsed to 58-5.
That they were eventually dismissed for 233 was largely due to Mahmudullah's run-a-ball 111.
But by the time the 37-year-old veteran completed just his fourth one-day international century in 195 innings, the match had long since ceased to be a contest, with no other Bangladesh batsman making more than 22.
South Africa have now won four of their opening five World Cup matches, with the only blot a shock loss to the Netherlands.
Bangladesh, by contrast, are struggling to qualify for the semi-finals following four defeats in five games and sit rock-bottom of the 10-team group.
An early double strike gave them brief hope of a fourth win in five ODIs against South Africa.
But left-handed opener De Kock responded with a third hundred in five World Cup innings -- after scores of 100 and 109 against Sri Lanka and Australia -- as he continued his superb start to what the 30-year-old has said will be his last major one-day tournament.
Heinrich Klaasen followed up with a rapid 90 just days after his 109 in South Africa's 229-run thrashing of reigning champions England at the Wankhede on Saturday.
A seven-strong Bangladesh attack, without the injured Taskin Ahmed, all suffered with pacemen Mustafizur Rahman and Shoriful Islam both conceding 76 runs from their nine-over spells.
Fit-again Bangladesh captain Shakib Al Hasan, appearing in his fifth World Cup, was not spared either during a return of 1-69 in nine overs.
- Mahmudullah century -
South Africa left-arm quick Marco Jansen then struck twice in two balls before Shakib survived the hat-trick.
Star all-rounder Shakib, however, had made just one when he was well caught by wicketkeeper Klaasen, off World Cup debutant Lizaad Williams.
It was Klaasen's third catch of the innings as he deputised behind the stumps for cramp victim De Kock.
Bangladesh were now in dire straits at 31-3 inside eight overs and were soon 58-5.
Mahmudullah, dropped on 75 when a back-pedalling Williams floored an awkward chance in the deep, delayed the inevitable loss with 11 fours and four sixes.
Earlier, Aiden Markram, again leading South Africa in place of ill regular skipper Temba Bavuma, unsurprisingly batted first upon winning the toss given the Proteas had posted a mammoth 399-7 after being sent in by England.
South Africa were faltering after Reeza Hendricks and Rassie van der Dussen fell in quick succession.
But Markram made a stylish 60 while helping De Kock turn the tide in a third-wicket stand of 131 before he tamely chipped Shakib to long-off.
De Kock, however, powered on and was in sight of becoming just the third batsman to score a World Cup double century when he sliced Hasan Mahmud to deep backward point.
He faced 140 balls in total, including 15 fours and seven sixes hat were a mixture of elegant strokeplay and sheer brute force.
Klaasen ensured there was no respite for Bangladesh with eight sixes in his 49-ball innings before he holed out in the last over.