Police say they are concerned about the possible spread of outlaw motorcycle gangs in Sydney's inner-west following a brawl between 30 men from rival groups at a cafe on a busy street in Burwood.
Violence erupted at the cafe on Burwood Road on Wednesday night after about 20 male diners were confronted by a group of about 10 men.
It's suspected the brawl involved members of two rival outlaw motorcycle gangs, the Rebels and Lone Wolves.
The two groups of men hurled tables and chairs at each other before fleeing the scene.
One man was treated at the scene for facial lacerations after being hit by a bottle, and was later taken to Concord Hospital.
Violence involving bikies is not foreign to the inner-west. In 2009, a Hells Angels clubhouse in Petersham was bombed.
But Detective Superintendent Mark Jones said it was "something that's a little foreign to Burwood".
"At this point in time, there's nothing we can say about whether there's actually any clubhouses in the area."
"But it's something that we are concerned about."
Witnesses to Wednesday night's brawl saw men fleeing in clothing that bore patches affiliated with the Rebels bikie gang.
"Some were wearing Rebels ... jackets and that sort of stuff," Burwood police duty officer Mark Scifleet told AAP.
"From that, we've pieced together (it's) probably between the Lone Wolves and the Rebels."
Police are trying to identify the man who was treated for facial injuries.
It's not clear if he was involved in the brawl or an innocent bystander.
CCTV footage is being reviewed to help police identify the men, and anyone with more information is urged to come forward.