The online footage shows a girl being dragged by her hair and forced to fight.
She is surrounded and repeatedly punched in the head as she tries to cover her face. Others kick her on the body.
At the end of the 1.07-minute video, the girl collapses on the roadside.
The Facebook posting, by 14-year-old Jayvin Ryder, comes with an introduction which says, "Ok everyone so over in Christchurch there has been a 4 on 1 beating that has caused lots of drama in Christchurch. Poor thing, she didn't even want it she was dragged into it! Like to support the poor girl.''
By late this afternoon it had received more than 41,000 likes and has been shared almost 2,600 times.
Meanwhile police had confirmed that three arrests were made following a fight in Papanui yesterday evening.
Police were called after reports of a fight in Papanui Domain about 6.20pm, involving between 10 and 15 people. It was believed weapons were used and that a car's windows had been smashed, Mr Keith said.
Two males, aged 17 and 18, were arrested and given pre-charge warnings for fighting. A third, aged 17, was arrested for possession of an offensive weapon and had been referred to the Community Justice Panel.
Police believed the fight had been prompted by Facebook posts calling for retaliation over the assault on a teenage girl on Saturday, however those arrested were not believed to have had any connection to that incident or to the people involved in it.