Police have arrested a 37-year-old woman after a Staffordshire bull terrier bit 11 children in a park.
The dog attacked children playing in Burns Avenue, Blyth, Northumberland, at 6.30pm on Wednesday, Northumbria Police said.
The terrier was caught and taken to secure kennels while attempts were made to find the owner.
A force spokesman said the woman was arrested on suspicion of having a dog dangerously out of control.
Fiona Richards, 33, who lives opposite the park, said her husband Brett helped restrain the dog after her daughter had run into the house screaming she had been bitten.
"We were indoors and she came screaming through the door saying that she had been bitten," she said.
"She said the dog was still biting people, so we told her to stay at the door and we ran over.
"My husband went straight in and there was already a dad in there trying to lift the kids out of harm's way.
"The dog was running around super-fast biting every kid in there, I saw it grab a little one by the shoulder.
"It was bedlam, they were all screaming and there were loads of kids as it's a new park."
Eventually her husband helped back the dog into a corner and they used their own doglead to tie it to the railings.
She said her daughter Isabel, 11, suffered puncture wounds to her thigh and was given antibiotics after being seen in hospital.
"It was so scary as the dog was contained within the park, so it had nowhere to go," she said.
"One of Isabel's friends is still in hospital and is going in for surgery."
Nine children were treated in hospital with bite injuries. Six were driven to hospital in Cramlington by relatives while three were taken to the Royal Victoria Infirmary, Newcastle, by the North East Ambulance Service.
None was thought to be seriously injured though three were kept in overnight.
The spokesman said: "Extra officers are in the area speaking with people and offering reassurance."
Anyone with concerns or any information is asked to contact police on 101.
Neil Wilkinson, 43, went straight into the park and lifted children to safety over the railings as the dog was running around.
"There was about 30 kids in there and the dog just arrived from nowhere," he said.
"I got in and started lifting them up and out of the park. As I was doing it the dog leapt up and bit my son on the arm."
He said Kayden, six, suffered a small puncture wound which he had bandaged.