A wild brawl at a McDonald's outlet in Melbourne's west between two packs of teenage youths was organised beforehand on Facebook, police believe.

Four boys were taken to hospital with various injuries, including stab wounds, after the fight in St Albans just before 6.15pm on Sunday.

The victims, all aged 17, are from Braybrook, North Melbourne, St Albans and Caroline Springs.

Between 20 and 30 people were involved in the all-in brawl, with some carrying knives and baseball bats.