A child's birthday party in western Sydney descended into a brawl on Saturday afternoon following a minor disagreement on the play equipment.
Three fathers had to be taken to hospital with minor injuries when a fight broke out between parents from two separate birthday parties being held at Lollipop's Playland & Cafe in Wetherill Park.
The incident started when children from each birthday party had a small fight over who could use the equipment at the indoor playground for kids aged two to 11.
One father then allegedly pulled the hair of a young girl, Fairfax Media has been told.
The girl left the playground to tell her father, aged 48, that a stranger had pulled her hair.
The father then confronted the man to discuss the incident but he was allegedly knocked to the ground and assaulted.
Two friends of the 48-year-old came to his aid but they were also allegedly assaulted, police said.
The father and his two friends, aged 27 and 32, were all taken to Fairfield Hospital with cuts and bruising to their faces, heads, backs and hands.
The rival group fled the scene in vehicles just after 4.30pm, police said.
Lollipop's Playland & Cafe, on McIlwraith Street, has provided CCTV to police and declined to comment.
The centre says it is a popular party venue for babies, toddlers and school aged kids with slides, ball pits, jumping castles and a tea cup ride.
Detectives from Fairfield have appealed for any witnesses to contact Crime Stoppers on 1800 333 000.