Martin Guptill's unbeaten century helped New Zealand level their three-match one-day international series against South Africa with a commanding eight-wicket win on Sunday.

The tourists capitalised on a poor battling display from South Africa to race to victory with 33 balls to spare, Guptill anchoring their chase with 103 off 134 deliveries as New Zealand reached 207-2.

Guptill's efforts – ably assisted by Tom Latham (64) – ensured a comfortable run chase for the Black Caps batsmen after their bowling unit had worked brilliantly.

Led by Dougie Bracewell (3-31) New Zealand kept things tight with disciplined bowling and, combined with some questionable batting, they dismissed the Proteas for 204.

New Zealand's victory never looked in doubt as their openers took any sting out of the South Africa attack, Guptill – who was dropped on three occasions – firing the winning runs to leave everything to play for in Durban on Wednesday.

Inside four overs South Africa's decision to bat looked questionable in Potchefstroom as Hashim Amla (8) and Morne van Wijk (2) had both fallen to Adam Milne (2-39).

Star batsman AB de Villiers' (31) third-wicket partnership with Rilee Rossouw (39) helped to steady the ship, but even the enigmatic batsman could not find his rhythm.

Unusually for De Villiers his 45-ball innings only included one boundary before he clipped Grant Elliott (1-25) to Guptill at mid-wicket.

His dismissal came soon after Rossouw and David Miller (5) had also departed, leaving a bleak outlook for the hosts on 107-5.

Farhaan Behardien (70) played a crucial knock to get De Villiers' side over 200 with five fours and one six, but his dismissal triggered a collapse at the end as four wickets fell for 16 runs.

New Zealand's innings showed far more poises as Guptill and Latham patiently put them in sight of victory, their 126-run opening partnership proving crucial.

While Guptill was generally conservative in his approach, he did allow the occasional attacking stroke as he blitzed three sixes and nine fours on his way to three figures.

His final boundary through extra cover brought up his ninth ODI century and also secured the win for New Zealand.