Police have confirmed they are also investigating after identifying those involved.
The video shows a girl in a red jacket dragging another girl by the hair, and a boy attempting to fend her off, saying "I don't wanna hurt no one. Let her f***en go".
"Hit me," the girl in the red jacket says, as the victim cowers behind the boy but he refuses, saying: "I'm not gonna hit you".
She then drags the the girl to the ground and begins kicking her. The boy bends over the girl and protects her head as the girl in the red jacket repeatedly knees him in the face.
A second girl, apparently the one who was originally filming, then jumps in and starts kicking and hitting the pair. An onlooker says the boy is bleeding.
Younger children can be seen watching in the background.
It appears the video was filmed outside Whakatane New World. MP Anne Tolley's electorate office is visible in the background.
Hundreds of commenters on Facebook were split between disgust at the girls' actions and commending the boy for his refusal to fight back.
But a Facebook post that appeared to be from one of the girls says someone took a swing at her and the boy was choking her before the filming began.
Eastern Bay of Plenty Area youth and community services supervisor Sergeant Thomas Brooks said the people in the video have been identified and police were making enquiries.