Portland police used pepper spray on demonstrators protesting cuts to social services in a Saturday rally that drew hundreds, reported The Oregonian.
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Police said pepper spray was used when officers clashed with demonstrators armed with wooden shields, according to the report. One person was arrested.
The event was led by Portland Action Lab, a group believed tied to the Occupy Portland movement, said the Associated Press.
The city's police bureau issued a statement saying organizers did not have permission to hold the march, which was held to protest financial cuts to social and public services.
"We thought it was important to have this rally right before the election to get these issues into the public consciousness and begin to organize against austerity measures," Portland Action Lab spokesman Nicholas Caleb told The Oregonian, adding that the group was not informed ahead of time that they needed a permit.
"We try to be peaceful," he said. "Protest in Portland is not violent. That they [the police] continue to use this much force is pretty unconscionable."
Police did not say how many people were pepper-sprayed, but the Oregonian said at least 20 people were hit, several of them teenagers.
Photojournalist Alex Milan Tracy shot this footage of the protests: