YOKOHAMA, Japan -- New Zealand straightened the world champion crown on its head and removed any doubt about its status as Rugby World Cup favourite as it overcame South Africa 23-13 on Saturday in the tournament's most anticipated pool game.

A resurgent South Africa drew with the All Blacks on their home turf in July and stripped them of the Rugby Championship to make many think the New Zealanders had been finally brought back to the field. They also lost the No. 1 ranking they'd held for a decade, but that's coming back to them after this win that showed off their ruthlessness and depth of skills.

After a cagey start, the All Blacks unlocked the scoreboard by exploiting Springboks errors for 17 points in six minutes to lead 17-3 at halftime. They then let South Africa back in with a soft try, and the Springboks closed within four points with a quarter to go.

But the All Blacks re-imposed control up front, if not on South Africa wisp Cheslin Kolbe, and two late penalties secured the victory to open their account in a bid for a third successive World Cup title.

"The defence of both sides was very staunch and you just had to take what you were given," New Zealand coach Steve Hansen said.

His side was stifled by South Africa's blitz defence for more than a quarter, but pounced on the Springboks' errors in possession.

A loose pass by scrumhalf Faf de Klerk was hacked on by New Zealand flyhalf Richie Mo'unga, who regathered and was caught in front of the posts by South Africa wing Makazole Mpimpi. South Africa was penalized and Mo'unga kicked the first points for New Zealand, which was energized.

A Duane Vermuelen knock on led to a Mo'unga cross-chip to unmarked wing Sevu Reece. He led a surge down the right touch line with support from Aaron Smith and Ardie Savea. Winger George Bridge then directed Beauden Barrett to take a half gap and Bridge was beside the fullback to take the offload and score.

Springboks flyhalf Handre Pollard then spilled another up-and-under and referee Jerome Garces played advantage. Center Anton Lienert-Brown received the ball squeezed in beside the left touch, turned inside, and cut past three defenders and slipped a fourth. He drew the last man and lock Scott Barrett loped to the posts.

Mo'unga converted both tries and the double strike in three minutes took the sting out of South Africa.

Even Springboks coach Rassie Erasmus was impressed.

"Sometimes when you play New Zealand you don't lose turnovers because you don't have as much ball," Erasmus said. "The few times we played with the ball they scored two tries from our turnovers and we weren't organized in defence. They were potent, that shows their class. New Zealand deserved to win even with tries from turnovers."

The All Blacks were paying the Springboks in kind by making more than 90 per cent of their tackles until seven minutes into the new half. A routine ruck set up by lock Eben Etzebeth wasn't covered, amazingly, at its most exposed point -- the middle. Flanker Pieter-Steph du Toit accepted the gap, stepped over Etzebeth, and ran untouched for a dive beside the posts.

Pollard's conversion closed the gap to seven points, and then four with a sweet dropped goal from 35 metres.

Kolbe, the smallest starter on the field, was just barely contained as he made three searing breaks on the right wing before cramp slowed him.

But the effort to play catch-up, and take risks that conceded nine penalties, played into the All Blacks' hands. Also, fresh legs helped New Zealand regain momentum, giving Mo'unga and Beauden Barrett late penalty kicks to put the score out of reach, and retain their perfect record in pool play, now 29-0 over the tournament's 32-year history.

"People forget that as well as New Zealand attack, they defend as well," Erasmus said. "The moment they get scoreboard pressure on you, they really make it tough. They pile pressure on you. But enough about them, we've got a hell of a lot of work to do."

They also have an injury concern. Reserve prop Trevor Nyakane came off with an ankle injury which Erasmus said was "fairly serious." Nyakane had just recovered from a knee injury.

New Zealand next plays in 11 days against Canada in Oita. South Africa has Namibia next Saturday in Toyota.