AAP

Adelaide police have arrested 12 men connected with two bikie gangs after a violent brawl at a city nightclub was captured by security cameras.

Police said 13 members of the Hells Angels and 12 members of the Finks clashed violently about 5am on May 29 at the Hindley Street venue.

They attacked each other with bottles, glasses, metal bollards and heavy metal bar stools, with several members of the group suffering serious head injuries.

Detective Inspector Steve Taylor, from the Crime Gangs Task Force, said the incident showed the true nature of the relationship between bikie gangs.

While they had recently portrayed themselves as law-abiding citizens who were united in the fight against SA's anti-gang laws, the opposite was actually the truth, he said.

"These pictures show members of motorcycle gangs are not ordinary citizens who ride motorcycles on weekends as a fun get together," Det Insp Taylor said.

"They are not unified, they are violent offenders who have no problem playing out their differences in public.

"This violence has included shootings, bombings and stabbings."

Det Insp Taylor said it was lucky no one was killed in the latest incident.

No arrests were made on the night, with police launching a major investigation involving about 170 officers.

They raided clubrooms operated by both the Finks and the Hells Angels on Friday.

Those arrested included seven members of the Finks, including the club's sergeant-at-arms, one member of the Hells Angels and four people associated with the Hells Angels.

They were all charged with aggravated riot, a recently introduced offence which carries a 10-year maximum jail term.

The 12 were granted police bail on strict conditions and will appear in court at a later date.