HUNDREDS of young people battled riot police in a university city in the north-west of the USA at the weekend.
The clashes took place in Eugene, Oregon, which has a longstanding anarchist presence.
Police used tear gas against the youngsters, who had been out partying.
Reported Fox 12: "Police say it's unclear what touched off a 400-strong riot in the college town of Eugene that led to nine arrests.
"No injuries were reported after people spilled out onto a residential street Friday night, throwing bottles at officers, breaking car windows and tearing down street signs in the town that's home to the University of
"Eugene police spokesman Doug Mozan says if people start to spill into the street and get drunk enough in the area home to many student renters, 'sometimes they engage in group-think.' He says 'it was like a flash mob, almost'."