A suspicious overnight fire in Adelaide has become the fourth incident linked to a feud between rival gangs over a substantial drug debt.
A hair salon at Seaton, west of the CBD, was damaged after reports a block of three businesses were set alight before 5am Wednesday.
The blaze comes after five shots were fired at an Ascot Park house on Monday night, a fire was deliberately lit at a gymnasium at Marleston on August 9 and another fire started in a food truck parked at a property at Mile End the day before.
Detective Superintendent Mark Trenwith said on Tuesday the attacks were part of "tit for tat" attacks involving members of the Hells Angels and another group.
He said it was also thought the incidents were sparked in part by a shift in the balance of power between the rival gangs after the arrest of five members of the Hells Angels recently over a 2012 murder.
The home where the food truck was burnt was linked to one of those men charged with the murder of spray painter Jason De Ieso.
Supt Trenwith said police were concerned at the very public displays of violence.
"Obviously we're concerned that firearms are being used, that premises are being torched," he said.
"The particular danger is that some innocent member of the public will get caught up in this."
Police said two people in the home at the time of Monday night's shooting were not involved in any criminality and were not hurt.