Police are hunting three men who set off fireworks in a sheep's mouth, slit its stomach, kicked it and dragged it down a track on the mountain at Mt Maunganui.

The "cowardly, despicable act" has been described as the worst case of animal cruelty in the region.

Police were called to Mauao about 10.30pm on Sunday after two people walking around the base track of the mountain saw three men kicking what they thought was a person on the ground.

When officers arrived, they discovered the dead sheep about 800m down the track on the main beach side.

The remains of fireworks were still in its mouth and its jaw had been blown away. Its stomach had been slit, it appeared to have been bashed with a blunt instrument and it had a wound on its torso indicating an attempt had been made to light its wool.

A trail of blood showed the sheep had been dragged along part of the track. It is unknown at which point of the prolonged assault it died.

A sniffer dog was bought in to try to locate the attackers but was unsuccessful. The witnesses were unable to give a description of the attackers.

Tauranga SPCA manager John Esdaile, a former police inspector in Auckland, said authorities had no information to lead them to the attackers so could only hope the public would come forward with information.

He pointed to the link between animal cruelty and abuse towards humans.

"These are the murderers and serial killers of our future, and the sexual predators.

"This is the normal start for these sorts of people, they never leave it at animals. They'll progress to other things which involve us."

In Tauranga late last year, someone rammed a nail through a cat's head, severed its tail and three paws and tied it to a street sign.

The injuries were believed to have been inflicted by a teenage boy - hours after he saw his father attacking a girlfriend.

Mauao park ranger Mark Ray missed a call on his cellphone about the attack about midnight. He learned what had happened only yesterday morning.

The sheep had been covered by rubbish bags and a colleague helped him carry it off the mountain. They disposed of it down an offal hole at a friend's farm.

"These people are sick," Mr Ray said. "There is no other word to describe it. It's just hideous to do that to an animal.

"I had a quick look under the bags, I saw its neck. It wasn't there. There was blood all over it. That's as much as I wanted to see."

The 200 council-owned sheep on the mountain are used to keep the grass down. Mr Ray said that in the three years he had been the park ranger, this was the first time an animal had been attacked.