Proteas build on advantage

New Zealand are in danger of a humiliating first Test defeat against South Africa.

The tourists find themselves 269 runs behind the hosts in their second innings on day two in Cape Town.

Captain Brendon McCullum and Dean Brownlie are at the crease for the Black Caps, who lost Martin Guptill for a duck and Kane Williamson for 15.

At 33 for two at tea and following their dismal first-innings showing of 45 all out - their third-lowest Test score - McCullum's side are facing a heavy defeat after the hosts posted 347 for eight declared.

The Black Caps made the ideal start in the first ball of the second over of the day as Trent Boult got one to nip back at Alviro Petersen, who could only get an inside edge on the delivery before the ball clattered into the stumps.

AB de Villiers, who began the day unbeaten on 19, was tentative, scoring his first boundary in the seventh over as the hosts attempted to build on what was already a significant first-innings lead.

The boundary kickstarted the scoring although the hosts suffered a blow in the 73rd over. Veteran seam bowler Chris Martin pitched one up which swung away from Faf du Plessis, with the batsman edging to Williamson in the slips for 15.

At 280 for four De Villiers and new batsman Dean Elgar, playing in just his second Test, built slowly until consecutive fours from the one-day skipper off Boult yielded 10 runs in the 82nd over.

However New Zealand struck again in the 89th over as Elgar, playing back, edged a rising Boult delivery to wicketkeeper BJ Watling who took a simple catch for 21.

De Villiers fell in just the second over after lunch for 67. Walking to the off side to create room on leg, he missed and Martin's delivery smashed into the top of middle stump.

The 38-year-old struck again in his next over with Robin Peterson the next South African to be bowled as his off stump was disturbed attempting to play a leg side shot.

This led to home captain Graeme Smith declaring, leaving New Zealand to bat out the remaining 56 overs of the day 302 runs behind.

A tough task was made even harder when opener Guptill was dismissed in the last ball of the first over, pushing a tame Dale Steyn leg-stump half-volley to Hashim Amla at mid-wicket.

Skipper McCullum and Williamson dug in, with just six runs coming in the first six overs before a Steyn half-volley was dispatched to the mid-off boundary by Williamson.

The Black Caps continued to build slowly and survived a review in the ninth over when South Africa felt that Williamson edged a Vernon Philander delivery to De Villiers, although nothing showed up on hotspot and the not-out decision stood.

After battling through 46 balls for 15 Williamson became the second New Zealander to needlessly lose his wicket playing away from his body to edge a wide Jacques Kallis delivery to Petersen at second slip.