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Trailing 16-2 at halftime the visitors stunned New Zealand with four tries in 17 minutes before former Kiwis wing David Fusitu'a sealed the result with his third four-pointer three minutes from fulltime, sending the 25,800 and predominantly red-clad sell-out Waikato Stadium crowd into raptures.
Former Kiwis utility Tui Lolohea also scored a try and booted a conversion while Sio Siua Taukeiaho kicked two conversions and a first-half penalty goal. For the Kiwis, wings Dallin Watene-Zelezniak and Jordan Rapana both scored while fullback Roger Tuivasa-Sheck finished with two tries.
The result makes Tonga the first second-tier nation to upset one of the three top-tier teams and skyrockets makes them genuine title contenders to Australia's crown, while leaving plenty of questions over the Kiwis remaining tournament prospects.
Tonga now progress through to a quarter final match-up with Lebanon in Christchurch next Saturday, while the Kiwis will face Fiji in Wellington - putting them on a crash course to meet the Kangaroos in the semi-finals.
Both sides kept straight faces during the build-up while denying any bad blood over four former New Zealand player choosing to play for the Pacific Island side, but the Kiwis made their feelings clear when captain Adam Blair led a fiery haka over halfway and up into the visitors faces, with the towering Nelson Asofa-Solomona shoving rival forward Andrew Fifita as the two sides separated.
Tonga responded in kind - and low and behold it was chief turncoat Taumalolo leading his side's Sipi Tau war cry - in his first public speaking appearance since arriving in Auckland two weeks ago.
Early on the Kiwis shelved the expansive style that defined their two tournament opening wins and had to absorb some sustained pressure before the visitors settled for a penalty to take the lead after seven minutes.
It took 12 minutes for the Kiwis to throw their first offload and two plays later a chance was missed with Rapana spilling a pass from Takairangi in the corner.
The arrival of Asofa-Solomona gave the Kiwis more momentum and a strong charge from the Melbourne giant featured in the lead-up to Watene-Zelezniak diving in for his first try in a Kiwis jersey at the end of the first quarter.
The Kiwis kept applying heat and found reward again with Rapana finishing in the corner before Johnson's conversion made it 10-2.
Tensions threatened to boil over after an Asofa-Solomona high shot but Tonga were unable to capitalise on the resulting penalty with Daniel Tupou denied a try due to a forward pass.
That proved to be a turning point and a tip-tackle from former Kiwis forward Manu Ma'u on Russell Packer soon after put New Zealand back in attacking range before Tuivasa-Sheck slipped through to score just before halftime.
Tonga came out firing after the resumption but missed two scoring chances before Fusitu'a claimed a crossfield kick to score out wide to make it 16-6.
Ten minutes later they were in again with Tupou scoring off an inside pass from Konrad Hurrell to help them to within four-points, and three minutes on they were in again with Packer gifting an ill-timed intercept pass for Lolohea to run in before Taukeiaho's conversion made it 18-16 inside the last quarter.
With their tails already up, Tonga's confidence skyrocketed when Hopoate dashed through. Although a second try to Tuivasa-Sheck kept the hosts within range, before Fusitu'a extinguished any hopes of a comeback.
Kiwis 22 (Dallin Watene-Zelezniak, Jordan Rapana, Roger Tuivasa-Sheck 2 tries, Shaun Johnson 3 cons)
Tonga 28 (David Fusitu'a 3, Tui Lolohea, Will Hopoate tries, Sio Siua Taukeiaho con, pen; Lolohea 2 cons)