Police are warning fans attending Rugby League World Cup 2017 matches they face being fined up to $5000 or jailed for up to three months if they invade the pitch.

Seven patrons, including a 15-year-old, were arrested after running onto the playing surface during the match between the Kiwis and Toa Samoa at Auckland's Mt Smart Stadium on Saturday night.

Six of them have been charged with pitch invasion and the 15-year-old referred to Police Youth Aid Section.

It is believed that all seven are from the same group.

Auckland City District Operation Commander Inspector Peter Gibson says under the Major Events Management Act, it is an offence to go onto the pitch or throw objects onto the playing surface at a major sporting event.

The New Zealand leg of Rugby League World Cup 2017 has been declared a major event under the Act.

'People who are foolish enough to consider invading the pitch at future matches should remember that this offence carries a penalty of up to three months' jail or a fine of up to $5000, as well as a potential criminal conviction.

'We will be enforcing the law on this rigorously during the tournament, and anyone who goes onto the pitch will be prosecuted.”

He says the incidents are disappointing, especially as the behaviour of the vast majority of the crowd at the match had been fantastic, with a strong family and community atmosphere.