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.

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.

“I thought it was an outstanding effort. There are some world class players in the Afghanistan side and they got off to a very good start,” Williamson said.

“In the end it was a brilliant effort to restrict them so fair play to the bowlers, and it was a very good performance with the bat.

“It's nice to have three wins on the board. Every game is tough and we'll need to adapt to beat India.”

Minnows Afghanistan have lost all three of their matches and captain Gulbadin Naib was critical of their efforts.

“We started really well and then we didn't take responsiblity. We missed out on length balls and gave away ugly wickets,” he fumed.

“We are not playing according to the plan, especially the batsmen. Our fielding has to improve.

“There is a lot of work to do to go to the next level.”

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.

Rashid unable to bowl

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.

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

Teams

New Zealand: Martin Guptill, Colin Munro, Kane Williamson (capt), Ross Taylor, Tom Latham (wkt), Jimmy Neesham, Colin de Grandhomme, Mitchell Santner, Matt Henry, Lockie Ferguson, Trent Boult

Afghanistan: Noor Ali Zadran, Hazratullah Zazai, Rahmat Shah, Hashmatullah Shahidi, Gulbadin Naib (capt), Najibullah Zadran, Mohammad Nabi, Rashid Khan, Ikram Alikhil (wkt), Aftab Alam, Hamid Hassan

Umpires: Aleem Dar (PAK) and Michael Gough (ENG) TV umpire: Richard Kettleborough (ENG) Match referee: Ranjan Madugalle (SRI)