Senior Sergeant Clive Wood said people "let off fireworks near a petrol station, threw missiles at police, obstructed roads and footpaths and behaved in a very disorderly manner" in Otahuhu's main shopping area after 9pm.
At one stage, an ambulance was prevented from getting to a medical emergency, he said.
"These people, who appeared to have no care for anyone's welfare, didn't think about the consequences of their actions and I do hope they take time out to reflect on how badly they behaved".
