Twenty people have been arrested and two hospitalised as some of the high-spirited celebrations turned sour after the Tonga-Australia rugby league test in Auckland on Saturday night.

A large brawl and "pockets of disorder" kept South Auckland police busy after the test at Mt Smart Stadium, won by Australia 34-16.

A police spokeswoman said there were 20 arrests made throughout the night and two people were taken to hospital with serious injuries after a large brawl on Nikau Rd which erupted towards the end of the test.

League fans had turned up in droves to watch the match - the first time the two sides had clashed in a rugby league test.

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Hundreds of people and cars were out in the streets surrounding the stadium and spilled farther afield into Mangere with "pockets of disorder" in various locations, the spokeswoman said.

"Two people were taken to hospital with serious injuries as a result of a large fight on Nikau Road which broke out around the end of the game," she said.

"Police is grateful to our partner agencies for their assistance over the night."

More than 26,000 Tongan fans packed into the sold-out stadium, some arriving as early as 9am to be a part of the action.

Mate Ma'a Tonga lost 34-16 to the world champions, Australia's Kangaroos.