New Zealand have beaten the best team in the Cricket World Cup, Kane Williamson claims, after the Black Caps edged a thrilling contest with Australia in Auckland.

After skittling their tournament co-hosts for 151, New Zealand looked well on course for victory, but the run chase was far from simple, Williamson hitting the winning runs after Australia had incredibly taken nine wickets.

Victory maintained the Kiwis perfect record in the tournament so far, and Williamson believes the victory may lay down a marker for the rest of the teams eyeing the trophy.

"Obviously Australia are number one in the world," Williamson said. "So whenever you play them, it's always a really tough match. 

"They'll never give you any easy runs with the bat or an easy wicket. So it's always tough to play them and great to get a win against the best team. 

"I think the opportunity to play them is always a good one because you learn a lot as well. 

"So that's a big thing for us to beat a team like that to move forward in this competition."

Trent Boult starred with the ball for New Zealand, taking 5-27 from his compliment of overs, and the left-arm quick paid tribute to the Auckland fans for creating a fearsome atmosphere.

"It was really incredible to be honest," he added. 

"To have a crowd right behind us was a team it was something really special. 

"On the wickets, you couldn't hear yourself think. It was an amazing atmosphere and a really good result for us."