Fly-half Manie Libbok was named man of the match as South Africa opened the defence of their Rugby World Cup title with victory over Scotland, as Wales held out against a spirited Fiji comeback.

Libbok's highlight was a second-half no-look assist for Kurt-Lee Arendse as the Springboks began their search for a record fourth Webb Ellis trophy in clinical fashion in the Marseille heat, winning 18-3.

Former World Player of the Year Pieter-Steph Du Toit had crashed over earlier in the tie for Jacques Nienaber's outfit in Pool B.

The reigning champions face Romania next, before taking on world number one side Ireland.

"I think it could have been a slippery one. Scotland are a good side, they are not number five in the world for nothing," Nienaber told media. "I thought we had a little bit of dominance in the first-half but we had to grind the win out."

Meanwhile, Wales began their campaign by overcoming Fiji 32-26 in Bordeaux, avoiding defeat to the highest ranked side in Pool C.

Winger Josh Adams claimed one of four tries for Wales as experienced fly-half Dan Biggar crossed the 100-point mark for his country at World Cups, surpassing Neil Jenkins' 98-point record.

"You can never write Fiji off. Right at the end they could have won the game," Adams told media after his side led by 18 points with less than a quarter of an hour to play.

"We don't want another game like that," he added before next Saturday's match with Portugal.

Fiji had launched a late comeback thanks to tries from Josua Tuisova and Mesake Doge in the final seven minutes but they were unable to repeat their famous 2007 World Cup victory over Wales.

Fiji will now have to target next Sunday's game with Australia if they are to keep alive their hopes of a first quarter-final spot in 16 years. (AFP)