Sixty Victorian properties linked to the Comancheros have been raided amid police fears of a payback involving the Hells Angels.
At least 18 people were arrested, including the Comancheros' Victorian vice president, when police swooped early Wednesday morning.
Firearms, drugs including large quantities of steroids, ammunition, cash, tasers, swords and explosives were seized at 58 of 62 addresses targeted.
The raided properties include clubhouses, homes, factories and businesses.
"There's still an ongoing feud with the Hells Angels motorcycle club and we've got pretty good intelligence they were planning retaliation for attacks on their premises last year," Assistant Commissioner Steve Fontana told reporters.
Properties linked to the Comancheros including a gym, clubhouse and vehicles were attacked with guns and explosives last year.
Mr Fontana said the Comancheros brokered a deal after police executed warrants on the Hells Angels and other bikie groups last year.
"That was fortunate that that took place but that hasn't resolved the issue between these clubs," he said.
"I understand that a couple of individuals are really dark on the fact those attacks took place on their clubhouse and their premises and they want to retaliate."
The Victorian Comancheros vice president was among those arrested and allegedly found to have a high-powered handgun and another firearm in his possession, Mr Fontana said.
The Comancheros were targeted after recent police operations in Mildura led to members being charged with serious offences.
"They absolutely terrorised the community," Mr Fontana said.
Police now believe the Rebels motorcycle gang are moving in on Mildura after police pushed the Comancheros out.
The Finks outlaw bikies also recently patched over to the Mongols Motorcycle Club with intelligence suggesting they will be a front for Middle Eastern crime rackets in Victoria, Mr Fontana said.
"They're linked back to NSW and we're not going to sit back and wait for this to happen," he said.
"I'm putting these clubs on notice that we'll be coming in hard and they'll see more of this activity."
