Emily Drumm scored a quick-fire century as New Zealand confirmed their place in the semi-finals with a convincing victory.

Buoyed by the support of the home crowd at Lincoln Green, the second favourites for the competition cruised home by 158 runs with 14 overs to spare.

After winning the toss, South Africa asked New Zealand to bat first, which proved to be a big mistake.

The home side rattled up 265 for five in their 50 overs, with skipper Drumm racing to an unbeaten 108 from just 104 balls.

She was well supported by Rebecca Rolls (44), Anna O'Leary (32) and Haidee Tiffen, who cracked 35 off 24 balls.

"We went up a gear today," said Drumm.

"We are getting used to playing at this sort of pace and it is nice that we can lift ourselves against the sides who would like to spoil the party for us."

South Africa made a disastrous start to their reply as they slumped to five for three with both openers were dismissed for ducks by Katrina Keenan.

Cindy Eksteen batted with skill and detrmination to make 44 not out, including seven fours, but only two other batsmen reached double figures.

Medium pacer Helen Watson swept through the tail for figures of three for 14 and the South African innings was forced to close early because Helen Davies was unable to bat due to a suspected broken finger.