A vicious dog attack on a pregnant woman only stopped once a neighbour rattled a fence to distract them.

It allowed her time to dial a pin code to unlock a door and seek refuge inside the house.

Initially alerted by the young woman's "blood curdling screams", neighbours climbed through a window to treat bloody wounds to her legs and arms.

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Emergency services were called to Glenrowan Ave, in Christchurch, about 7.30pm Tuesday after a dog attack on a woman, believed to be 23 years old and 30 weeks' pregnant.

The two dogs involved – described as staffordshire, terrier and mastiff-type breeds – were unregistered.

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ALICE CANNET/Stuff.co.nz Kiwis say we have to be cautious around potentially dangerous dogs but they shouldn't be banned.

A tenant said the young female dog, Narla, was on heat, and was the aggressor in the attack. He claimed his own dog, Deizel, tried to defend the woman as she fought off Narla in the dark.

Narla was a stray dog rescued from the red zone five months ago. She belonged to a friend who dropped her at the house at the weekend to breed with Deizel – a 2-year-old staffordshire bull terrier.

Neighbour Linda Steven was in her garage before other residents came streaming our of their houses.

"We heard heard these blood-curdling screams, I thought it was the dogs fighting and the kids shouting."

STOCK IMAGE It is the third serious dog attack in Christchurch since last Thursday.

Corye Whyte, who lived next to the property, ran outside and tried to lure the dogs away from the woman, who was home alone at the time.

"We started banging on the gate just to get the dog away from her just to give her enough time to get inside. It worked. And then, as soon as she was inside that's when we rung the ambulance."

The woman, who was heading from a modified granny flat at the rear of the property into the house, dialled a pin code to unlock the door and escape the attack.

The dogs were behind a fence, but there was no access to the house from the front yard. Whyte and others climbed in through the front window to treat her.

"It was pretty messy. There was a lot of blood. One foot was pretty bad, and her other one had a couple of bite [marks] on it, and her forearm had a bite, and the [other arm] had a couple of puncture wounds."

Whyte, who once bred staffordshire dogs, said Narla was "more involved" than Deizel.

[Deizel] doesn't have a nature of biting, kids can jump all over him and stuff like that.

"It was more [Narla]. Because she was on heat I think it was more the excitement sort of thing. The owner of the older dog didn't know the nature of [her]."

TENANT DEFENDS DOG

Deizel's owner believed his dog tried to defend the woman from Narla, who had earlier broken free from a collar used to tie her up.

He said the woman received a "small bite" from Deizel during attack, but he believed it was accidental as he tried to fend Narla off.

"Deizel was trying to defend her, and he's realised f... that's a human hand and let her go. He's carried on and pushed the other dog. If Deizel was involved, the injuries would have been absolutely tremendous."

He said he earlier warned his flatmates "don't trust" Narla because of her rough background, including a period as a stray dog in the Avondale red zone.

In the days leading up the attack, Narla was aggressive towards another flatmate. Deizel bit her to defend him, the man said.

"The only way Deizel will be put down is if it's court-ordered."

DOGS SEIZED

The Christchurch City Council said it received a complaint a woman was attacked by "a dog or dogs".

A spokeswoman said the council had seized both dogs. It had no record of either dog, as they were not micro-chipped or registered.

"Council has not received or obtained formal statements from either the victim or dog owner at this stage."

Acting Senior Sergeant Kath Pomfrett said police helped ambulance staff climb through a window to get to the woman. She had bites to both legs and an arm.

"Animal control are investigating further in regards to potential prosecution," she said.

In 2015, the Christchurch City Council's 11 field animal management officers responded to 1276 priority one dog complaints, which included attacks on people.

National debate has recently reignited over banning dangerous dog breeds after a spate of attacks.

A pit bull staffordshire cross was destroyed after mauling Caleb Ross, 2, at his Woolston home on Friday. The boy was rushed to hospital with three "deep bites" to the upper left part of his head.

He received seven stitches and was discharged on Sunday.

The attack happened just a day before 7-year-old Darnell Mikaere Minarapa-Brown was mauled by his uncle's pit bull terrier in Auckland.

A 72-year-old woman was set upon by a dog last Thursday, while cycling near her Christchurch home. She sustained serious leg injuries and had to undergo surgery, including a skin graft that transferred skin from her left thigh to the site of the wound on her left shin.