Up to 30 people were involved in fighting along Palmyra Avenue, centred on a football pitch at Peter Van Hasselt Park, from about 4.30pm on Sunday.
Weapons including a football corner post, a chisel, a spanner and knife were seized by police.
Three people were taken to Westmead Hospital and two to Nepean. One remained under police guard last night.
The football pitch at Peter Van Hasselt Park is being used South Sudan Football Association of NSW, a competition catering for young footballers of African descent.
Police established a two-kilometre-long crime scene, stretching from Forrester Road in Lethbridge Park to Van Diemans Avenue in Wilmot.
Five cars were impounded along the route, and numerous items of clothing were seized for forensic examination.
The brawl included males and females from their late teens to early 20s, police said.
Investigators urged anyone that witnessed the incident to come forward if they have not yet spoken to police.
It came a day after a man was assaulted with a cricket stump at a local cricket match in Bossley Park.
Source: Sydney Morning Herald