Will fight against India: Du Plessis

Bangladesh made the perfect start to their World Cup campaign as their highest one-day international score inspired a 21-run win over a beleaguered South Africa on Sunday.

Mashrafe Mortaza's side posted 330 for six as Mushfiqur Rahim (78) and Shakib Al Hasan (75) laid the foundations of their impressive display at the Oval.

Attempting to become the first team to successfully chase more than 330 to win a World Cup match, South Africa fell short t 309 for eight.

After reaching the World Cup quarter-finals in 2015, Bangladesh again look capable of shaking up cricket's established order, to the delight of their army of vociferous supporters who packed the Oval.

"It will be one of our top wins," Shakib Al Hasan, who received the player-of-the-match award for his all-round performance, said. "We have done some upsets at World Cups but we want to prove something at this tournament."

In contrast to Bangladesh's brilliant start, South Africa find themselves in turmoil after Du Plessis' decision to bowl first backfired despite two wickets from veteran spinner Imran Tahir in his 100th ODI appearance.

With the World Cup just four days old, they have already lost twice in south London -- this disappointing performance following their 104-run thrashing by hosts England.

South Africa, who have never won the World Cup, are left with little margin for error in the rest of the 10-team round-robin group stage.

It won't get any easier for the Proteas in their next match when they face title contenders India on Wednesday.

With Dale Steyn once again sidelined by a shoulder injury, South Africa suffered a fresh blow when fellow paceman Lungi Ngidi limped off with a reported hamstring problem after bowling just four overs on Sunday.

However, despite their back-to-back defeats and injury worries, Du Plessis has vowed to fight back.

"We're a proud sporting nation. The skills weren't here today but I can promise there will be fight against India on Wednesday. We're only firing at 50-60 percent and it shows that even Bangladesh can beat that," the South Africa captain said.