Japan pulled off the biggest shock in Rugby World Cup history as they defeated two-time champions South Africa 34-32 in a truly sensational Pool B clash.

Brighton's American Express Community Stadium was expected to play host to a routine triumph for the Springboks on Saturday, with Japan having failed to win their previous 18 World Cup outings.

However, Eddie Jones' men comfortably exceeded expectations with an outstanding performance and snatched the most unlikely of victories with a dramatic injury-time score from Karne Hesketh - after twice declining to kick at goal when a penalty would have tied the scores.

Full-back Ayumu Goromaru was responsible for 24 of Japan's points, but it was a tenacious and high-octane team effort that enabled the underdogs to claim a success that will live long in the memory.

And Pool B now appears wide open, with this astonishing shock result of potentially great significance to Scotland and Samoa, who were expected to battle for second place behind the Springboks.

The pace of Japan's early play appeared to surprise the Springboks and Goromaru kicked his first penalty before Francois Louw was driven over for the game's opening try in the 18th minute, with Pat Lambie adding the extras.

Japan hit back impressively and got over at the second attempt from a rolling maul of their own to retake the lead - skipper Michael Leitch the man to touch down after Hendrik Tui had been denied by the television match official.

However, South Africa were not behind for long - a familiar theme repeated as Bismarck du Plessis benefitted from another mass drive to crash over and make it 12-10.

Japan were far from finished and moved ahead again early in the second half through another Goromaru three-pointer.

Lood de Jager responded almost immediately with a bullocking run through a gap in the opposition defence for South Africa's third try, converted by Lambie, but two more Goromaru penalties levelled the score. 

Having refused opportunities to kick for goal in the first period, the Springboks gratefully accepted three points through Lambie in the 57th minute, only for Goromaru to respond in kind.

South Africa captain Jean de Villiers administered some stern words to his players as Goromaru lined up his sixth successful kick from seven attempts, and the impromptu team-talk appeared to have the desired effect as replacement hooker Adriaan Strauss crossed following a powerful run and surprisingly nifty sidestep.

Yet Japan somehow came back again after surviving a period of pressure, Goromaru finishing a flowing midfield move on the right before converting to make it 29-29.

Handre Pollard kicked South Africa in front once more with eight minutes to go, but there was to be a remarkable finale as Japan camped on their opponents' line and twice turned down the opportunity to draw level from the tee.

Their bravery was rewarded when South Africa, down to 14 following the sin-binning of Coenie Oosthuizen, eventually gave up space on their right flank and Hesketh capitalised to spark scenes of incredulous jubilation.