World champions New Zealand stretched out to a comprehensive 62-point winning margin over lowly Namibia, but only after the underdogs had held them up with a brave first-half display.

With 35 minutes gone, Namibia, ranked 23rd in the world, were within one point of the three-time winners.

But the All Blacks were in clinical mood in the second half, finishing with 11 tries.

New Zealand will top Pool B if they beat Italy next weekend.

That would set up a quarter-final against the runners-up of Pool A, which is boiling down to a three-way fight between Japan, Ireland and Scotland.

Namibia defy rankings and expectations

Pre-match expectations of a New Zealand rout were initially confounded as Namibia, the lowest-ranked side in the tournament, showed no sign of being awed by the prospect of taking on the world number one side.

To the delight of Welsh coach Phil Davies, the underdogs scored the first points of the match when impressive scrum-half Damian Stevens landed a penalty from out wide.

As well as a fast defensive line and a determination to get involved in the breakdown, Namibia showed some slick hands and incisive lines to make regular incursions into the All Blacks defence.

Hooker Torsten van Jaarsveld led the way for Namibia as they stayed close, before replacement prop Angus Ta'avao and full-back Ben Smith went over just before the break to give New Zealand a more comfortable 15-point cushion at the break.

All Blacks revitalised after second half

New Zealand coach Steve Hansen, who gave Brodie Retallick his planned 30-minute outing on his first appearance since suffering a shoulder injury in July, seemed to fire up his side for the second half.

Prop Joe Moody went over within two minutes of the restart, the first of seven second-half tries as New Zealand pared their game down to basics to grind down Namibia.

TJ Perenara saved the best score for last as he and fellow replacement Brad Weber exchanged extravagant offloads - Weber's being a behind-the-back pass - before diving into the corner to dot down. A packed Tokyo Stadium stood to pay tribute to both sides on the final whistle after an entertaining encounter.

'We had poor attitude' - what they said

New Zealand coach Steve Hansen: "The first half was pretty disappointing. We didn't turn up with the right attitude and Namibia made us pay for that. It's a good lesson, isn't it?

"Second half, there was pretty good stuff in it. I was really pleased with Jordie Barrett at 10, [he] played very, very well.

"To be the third-choice first-five [fly-half], and our two superstar first-fives not playing, he got us round the back well. We ended up scoring tries so there's a lot to like about it.

"It didn't happen in the first half because we had a poor attitude. They had more intent than us and played better than us in the first half."

Namibia coach Phil Davies: "We were just pleased that what we talked about before the game we were actually doing on the field against the best team in the world. So we're really pleased.

"The scoreboard's not very pretty at the end but the effort and the commitment ... so proud of the players with how we tried to play and certain things that we actually did, which is pleasing."

New Zealand: Smith, Reece, Goodhue, Lienert-Brown, Bridge; J Barrett, Smith; Moody, Taylor, Laulala, Retallick, Whitelock, Frizell, Cane, Savea.

Replacements: Coles, Tuungafasi, Ta'avao, Tuipulotu, Todd, Weber, Perenara, Ioane.

Namibia: Tromp, Klim, Newman, Deysel, Greyling; Kisting, Stevens; Rademeyer, Van Jaarsveld, De Klerk, Van Lill, Uanivi, Gaoseb, Forbes, Venter.

Replacements: Nortje, Theron, Coetzee, Retief, Booysen, Jantjies, De La Harpe, Du Toit