Three people taken to hospital after a fight erupts during a six-year-old's birthday party at a play centre in Sydney's Wetherill Park on Sunday.

A seven-year-old girl's tears after a man pulled her hair set in motion an alarming brawl at a children's play space that left three fathers in hospital.

The girl's uncle, Chris, has described the events leading up to the violence at Lollipop's Playland & Cafe in Sydney, Australia, on Saturday afternoon.

Chris was celebrating his son's birthday party with his extended family when his niece came running out of the jungle gym crying hysterically.

A screengrab of the brawl inside Lollipop's Playland & Cafe.

A horrific fight between parents attending separate birthday parties followed that put Chris, his own father and his cousin in hospital.

"Basically my niece came up to us crying. She was hysterical and shaking. I'd never seen her like that," said Chris, who requested his surname be withheld.

"She said to me and her father: 'a man pulled my hair'".

A screengrab of the brawl inside Lollipop's Playland & Cafe.

The girl's father and uncle couldn't believe a man would have done such a thing, and asked if she meant a boy had pulled her hair.

"But she said 'no, it was a man,' and she pointed out this guy," Chris said.

Chris' niece gestured to a man standing amongst another party group at the play space.

"We approached him and he said, no he didn't pull my hair, but my niece said 'yes, you did. Don't lie to my daddy.'"

Chris said the man then admitted to pulling the girl's hair.

"He said 'you bumped my daughter so I pulled your hair,'" Chris said.

"He said 'I'm going to kill you,' to my niece," Chris alleged.

"It's just horrific. It's barbaric," he said.

Chris alleges the man's friends then attacked him.

"They dragged me … maybe five metres from my cousin, the girls' father. Then they started attacking me and I braced myself and tried to block punches and kicks … they pushed me to the floor and kicked me in the head and my back and ribs and they just didn't stop," he said.

Footage captured on a mobile phone shows adults and children screaming as a man believed to be the girl's father is slammed to the ground and repeatedly punched, kicked and attacked with a chair.

Children as young as two hid in the jungle gym. Dozens more stood just metres away, watching the fracas, terrified.

"Being there and hearing the screams of the children ... the noise was horrendous," Chris said. "It'll be stuck in my head for a long time."

Inspector Maharaj said the police had obtained CCTV footage and other material from the playground operators and were still trying to identify the perpetrators, who ran off before officers attended the scene.

"I've got bruises all over my body and bumps all over my head. I've still got scans to go to to make sure nothing is dislocated and broken," Chris said.

His four-year-old son and five-year-old daughter were traumatised after witnessing the alleged attack, he said.

"My kids are terrified," Chris said. "They need me to put them to sleep and lay down with them. My daughter hasn't been to school. We're going to go to a counsellor tomorrow morning.

"Seeing your kids go through that - you can't do anything you're powerless," he said.

"It's not the case of wrong place wrong time." Chris said. "We were at a good place; it's a kids' playground. My son didn't even get to cut his cake."

The Lollipop's Playland and Cafe Franchise Managing Director Tim Newman-Morris said the brawl was "deeply troubling".

Newman-Morris said he had never seen such "unacceptable" behaviour from parents in his 15 years in the children's playground business.

"We have 31 centres in three countries [Australia, New Zealand and Indonesia], and we have over 2 million guests per year," Newman-Morris said. "Never before have we seen anything like this."

The centre promotes itself as a popular party venue for babies, toddlers and school-aged children with slides, ball pits, jumping castles and a tea-cup ride.

The police have urged the perpetrators to hand themselves in.