Police were called to a disturbance in the Auckland suburb of Otahuhu after league fans took to the streets on Saturday night.
A Tonga Invitational XIII took on Great Britain in Hamilton, overpowering the northerners 14-6.
Disorderly behaviour and fighting after the match resulted in an assault, with one fan receiving serious injuries, they told Newshub.
The throng of fans blocked roads and disrupted traffic.
Previous Tonga matches have been marred by violence in south Auckland. During 2017's World Cup, police warned locals to avoid the city centre.
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Manukau Ward Councillor Alf Filipaina in June said it was a minority of fans causing problems.
"Our community should say we do not put up with a very small group of people spoiling it for everybody. I'm hoping that the people who went out just to cause problems now realise that it is about the love of rugby league."