A Tokoroa police officer underwent surgery at the weekend after he was attacked by a dog while attending a call out.
Three officers were called to address in Tokoroa in the early hours of Saturday to arrest a man on a family violence matter.
A police spokesman said the man resisted arrest and at this point a dog on the property attacked one of the officers.
That officer managed to Taser the dog which is now impounded. The officer has undergone surgery in Waikato Hospital for leg injuries and may require further surgery. He remains in hospital.
There is no suggestion the dog was deliberately set on the officer.
The breed of dog is unknown at this stage but is described as a large mixed breed.