Kane Williamson led by example as the New Zealand captain's 79 not out guided his side to a seven-wicket win over Afghanistan that maintained their 100 percent start to the World Cup on Saturday.

Williamson was New Zealand's top scorer with a 99-ball innings containing nine fours after Jimmy Neesham took career-best one-day figures of 5-31 to dismiss Afghanistan for 172 at Taunton.

New Zealand's third successive victory kept them on course to make the semi-finals in the 10-team tournament, while minnows Afghanistan have lost all three of their matches.

New Zealand, who saw off Sri Lanka and Bangladesh in their opening two games, have won 11 of their last 12 World Cup games, with their only defeat in that span coming against Australia in the 2015 final.

The Black Caps' run chase got off to the worst possible start when Aftab Alam had Martin Guptill caught off a thin inside edge with the first ball of the innings. Guptill's 14th ODI duck was a dream start for Aftab in the pace bowler's first appearance in this year's World Cup.

Afghanistan took the field without leg-spinner Rashid Khan, who was hit on the head when he was dismissed by Lockie Ferguson's bouncer in the first innings.

He looked dazed as he walked off the field and later failed his first concussion test, ruling him out for the rest of the match and depriving Afghanistan of their best bowler.

But it was Aftab who was leading the Afghan attack to good effect and he removed Colin Munro to leave New Zealand on 41-2.

It was a nervous start from the Black Caps and Williamson had to survive a review of a caught behind appeal.

Afghanistan kept the pressure on and Williamson rode his luck again when he just made his ground to beat a run-out review.

Together with Ross Taylor, Williamson steadied the ship in a 89-run partnership for the third wicket.

It was hardly flashy stuff as they nudged singles and picked off the occasional four until Taylor was bowled by Aftab for 48 from 52 balls.

Fittingly, it was Williamson who clinched the win with a routine single as New Zealand reached 173-3 in 32.1 overs.

Earlier, Neesham turned the game in New Zealand's favour with his impressive spell after Afghanistan briefly threatened to rock the Black Caps.

Put in to bat, Afghanistan openers Hazratullah Zazai and Noor Ali Zadran blasted a quickfire 66 for the first wicket.

But pace bowler Neesham, who had struggled in New Zealand's first two matches, finally found his rhythm despite two rain interruptions.

Neesham made the crucial breakthrough when Hazratullah went for one big shot too many, the left-hander hitting to Colin Munro at deep cover to depart for 34.

Afghanistan lost their third wicket with the score still on 66 when Rahmat Shah was dismissed for a duck after a leading edge off Neesham was held by Guptill.

When Gulbadin Naib failed with a review attempt to overturn his edge behind off Neesham, Afghanistan had lost four wickets for four runs in 21 deliveries.

Hashmatullah Shahidi (59) top-scored for Afghanistan, but Neesham and Ferguson, who finished with 4-37, were too hot to handle.

Feature image courtesy: AFP Photo/ Saeed Khan