Reigning champions South Africa have been knocked out of the ICC U19 World Cup in Bangladesh following a shock two-wicket loss to Namibia on Sunday.

The young Proteas lost their opening game of the tournament to Bangladesh and needed to defeat Namibia to remain in with a chance of back-to-back titles.

But a dramatic batting collapse – they slumped to 8-60 at one stage - meant they could only manage 9-139 from their 50 overs and Namibia overcame a few late nerves to overtake that score in the 40th over.

THAT feeling of knocking the Reigning World Champions out of #U19CWC! Congratulations Namibia!https://t.co/aUdi77hqkO — ICC (@ICC) January 31, 2016

South Africa captain Tony de Zorzi blamed his side's top order for the defeat and said the result was extremely disappointing.

"We've let the country down in a massive way in not making it out of even the group stage," he said.

"The top order failed us completely, we were quite lucky to get to 130-odd and although we bowled quite well to try and restrict them, defending that kind of score on a flat deck was never going to be easy, we just couldn't win.

"The best thing we can do now is finish in the highest position we can and bring back a semblance of pride for our country, more than that, we can't do."

South Africa will take on Scotland in their final group game on Tuesday and need to win that clash to avoid finishing on the bottom of their group.

Coach Lawrence Mahatlane said there was still plenty to play for against Scotland, with pride on the line ahead of the Plate Championship portion of the tournament where all countries that don't make it out of the group stages play.

"Part of under-19 age group cricket is about learning and the key is taking the learnings forward and showing some improvement in the next few games," Mahatlane said.

"A couple of losses doesn't make them bad cricketers. They have a lot of talent and they need to make sure that they show that talent in the next few days and really back themselves."