Neighbours heard violent screams as a woman was attacked in her house in Hamilton late on Sunday night.
The 23-year-old woman was assaulted by an intruder after she went to investigate noises coming from the third floor of her home.
A man wearing a black balaclava, and black hooded sweatshirt with a white face skull-head pattern on the back of it hit her over the head with a long metal pole or bar with a hook on the end of it.
The woman screamed, ran down the stairs and the man chased her outside where he assaulted her again, only fleeing when a neighbour came to assist the woman.
A family who lived close by said they heard a woman screaming for about five minutes and went outside where a large crowd had gathered.
The neighbour said it felt like the woman was screaming "for ages" and they initially thought she had been attacked by a hammer.
Neighbours then saw two men running down a neighbouring driveway and jump a fence onto Edgecumbe Park.
Police and St John arrived shortly after. The victim is currently in Waikato Hospital undergoing surgery.
Hamilton detective sergeant Terri Wilson said while a number of neighbours heard the woman's screams, only the immediate neighbour rushed over to help her.
Mr Wilson said the woman was recovering well at Waikato Hopsital and expected to be discharged today following minor surgery on her hand as a result of the assault.
"Unfortunately a number of people heard the screams, but there was only one that went to assist the victim."
Mr Wilson said the neighbour had done the right thing in helping the victim although it may have seemed scary. She had been interviewed by police, but the offenders had fled the scene by the time she arrived to help.
The victim had only spoken to police officers briefly on the night of the incident and they hoped to confirm more with her tomorrow morning, as there were conflicting reports from neighbours about how many offenders were involved.
Police said the logical place for the offender to escape to would have been the nearby Edgecumbe Park, but a search of the area did not find a weapon, which had been described as a long pole with a hook.
A full scene investigation was carried out on Monday and neighbours were interviewed.
At this stage there were a number of unknowns including how many offenders were involved, whether the offender was known to her and what her living situation was.
Anyone with information is asked to contact Hamilton police on 07 858 6200.
Information can also be provided anonymously to 'Crimestoppers' on 0800 555