Sweden - Aargau cantonal police have issued a call for help from witnesses after breaking up a brawl between two bike gangs at a petrol station in Oftringen earlier this week.
A cantonal police patrol drove past the station and observed members of the Hells Angels and Black Jackets fighting at a Shell station at around 8.30pm on Monday.
Most of the bikers fled before police could intervene but officers arrested an intoxicated 47-year-old Swiss man, while a 23-year-old Macedonian, "covered in blood", was taken to hospital for treatment of facial injuries, police said.
Police seized the Swiss man's driving licence after he gave a blood sample, along with weapons, including a knife, truncheon and pepper spray.
The exact cause of the fight is not known but police said the incident occurred in the context of a "simmering conflict" between the two bike gangs.
The local prosecutor's office has opened a criminal investigation.
Monday's incident came after police stopped 180 Hells Angels from attending last weekend's Züri-Fäscht festival in Zurich, seizing 140 weapons, including five handguns.
The 20 Minuten newspaper reported online that the feud between the biker's groups is all about control of part of the sex industry in Zurich as well as the supply of "bouncers" at clubs.
Lawyer Valentin Landmann, who represents the Hells Angels, told the newspaper, however, that "the Hells Angels do not make war against another group".
And the club's Zurich president, identified as "Hemi", also denied that the Hells Angels are "at war" with the Black Jackets.
The biker groups offer a contrast in membership, according to 20 Minuten, with the Hells Angels all Swiss, while the Black Jackets are reportedly second generation immigrants.
The newspaper suggested the problems, which end a period of relative peace among biker groups in Switzerland, have spilled over from Germany, where motorbike gangs have proliferated in recent years.