Police are calling for a man who seriously injured a female officer in south Auckland to turn himself in, saying he's a thug and a coward.

The policewoman was struck from behind and knocked unconscious during disorder at a post-rugby league celebrations in the Otahuhu township on Saturday night.

She is now recovering at home from head and arm injuries.

The officer and four others had been dealing with group of rowdy partygoers who began throwing bottles at police during an arrest, Inspector Naila Hassan told Radio NZ on Monday.

There had been about 15 men inciting violence and goading other fans and it was not clear who had stuck the officer as police tried to speak to the group.

"It was quite a dynamic situation," Insp Hassan said.

"We would urge anyone who was in that group, and particularly the thug, and what I could call a coward, the coward who hit this officer to come forward and do the right thing."

Police are reviewing camera footage from the event but say the area was not well lit.