The property is advertised as a boxing/mixed martial arts gym open to the public.
The assaults, which allegedly took place on March 21, happened outside a bar on Victoria St.
Detective Senior Sergeant Colin Baillie said the victims were innocent members of the public having a good night in town with friends.
"One of the victims, a young father, suffered a serious brain injury and will likely have lifelong injuries due to the assault.
"Police would like to thank those brave members of the public who intervened on the night of the assaults and those have come forward with information."
The three men arrested this morning will be appearing in the Christchurch District Court today facing serious assault charges and participating in an organised criminal group.
"The investigation is ongoing and more arrests are likely."
Anyone who witnessed the assaults or has information in relation to them is encouraged to call police on 105 and quote file number 210321/2258 or Crimestoppers on 0800 555 111.
At least half a dozen armed officers descended on a Clissold St property in Merivale at about 7.45am on Friday.
A neighbour on Winchester St said the raid took place in what is usually a very quiet part of the city.
But she said she has been previously "woken by screams and shouts coming from the house".