Kiwis in front after controversial day

Kane Williamson has notched a record-equalling 17th Test century for New Zealand as his Test side secured the upper hand on a day three that was tinged with controversy in the series decider against South Africa in Hamilton.

The 26-year-old skipper spanked an unbeaten 148 off 216 balls at Seddon Park on Monday, including 14 boundaries and three sixes, as the Kiwis ended day three on 4-321 and a lead of seven runs.

Williamson's ton, earned from 150 balls, equals the legendary Martin Crowe's 22-year record of 17 Test centuries, earned between 1982 and 1995.

The injured Ross Taylor sits one back with 16 Test triple-figures.

The other talking point of the day came midway through the second session, when Australian umpires Rod Tucker and Bruce Oxenford ordered the ball changed after appearing concerned by South African attempts to scuff one side by throwing it on the bounce to wicketkeeper Quinton de Kock.

Tucker and Oxenford ordered the ball changed after a particularly egregious example of the throwing technique in the 59th over, earning the ire of Proteas skipper Faf du Plessis and paceman Vernon Philander in the process.

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Du Plessis has already been found guilty of ball tampering this summer, having been caught applying saliva to the ball with a mint in his mouth in November against Australia.

For the Black Caps, opener Jeet Raval knocked up a patient 88 off 254, serving as Williamson's anchor in a 190-run stand before wasting his wicket late in the afternoon.

Facing a Morne Morkel delivery as the light began to dim, Raval edged his attempted block to a diving de Kock behind the stumps.

Tom Latham had earlier gotten the form monkey off his back with a solid 50 before being removed by Morkel in the exact same fashion.

He and Raval enjoyed a productive first-wicket stand of 83, standing in stark contrast to their efforts in the first two Tests, where they maxed out with 16-run partnerships.

Neil Broom and Henry Nicholls fell limply before the close of play, while Mitch Santner survived a no-ball wicket by Philander to be 13 not out at the close.

New Zealand thus hold all the cards heading into the second-last day as the upper-order's efforts hand them a seven-run lead over South Africa's first-innings 314, with six wickets still up their sleeve.

Predicted heavy rainfall in the Waikato has also failed to eventuate, handing the Black Caps valuable batting time and the opportunity to avoid a series-losing draw.

However the recriminations of Monday's Test action may be yet to truly bear out, with the ball-tampering controversy likely to be played out over the coming days.

New Zealand XI: Tom Latham, Jeet Raval, Kane Williamson (c), Neil Broom, Henry Nicholls, Mitch Santner, BJ Watling (wk), Colin de Grandhomme, Matt Henry, Jeetan Patel, Neil Wagner.

South Africa XI: Theunis de Bruyn, Dean Elgar, Hashim Amla, JP Duminy, Faf du Plessis (c), Temba Bavuma, Quinton de Kock (wk), Vernon Philander, Keshav Maharaj, Morne Morkel, Kagiso Rabada.