Oregon police and National Guard troops in camouflage trucks pursued far-left protesters around the US city of Portland as a riot was declared late Wednesday, making at least 10 arrests.
The northwestern city that has seen continuous protests since summer had been placed on high alert by Governor Kate Brown, who extended an election-night emergency order amid fears of violent clashes over the contested US polls.
A heavy law enforcement presence flooded the streets after a handful of demonstrators broke off from hundreds-strong anti-Trump protests to shatter storefront windows, and a man believed to have thrown a Molotov cocktail was arrested.
The Multnomah County Sheriff's Office cited "widespread violence" in the city's downtown area, including glass bottles thrown at police who advanced on demonstrators.
An AFP journalist at the scene witnessed two arrests during a skirmish on a street corner that left protester Michael Ream with a bloodied face.
"It's the same thing it always is -- just horrible conduct of the police force and the terrible legacy that they carry every day," the 38-year-old PhD student told AFP as police handcuffed him.
Asked whether this week's contested election had brought him to the streets, he replied: "More or less. I mean, I haven't been out (protesting) in a while."
Portland has seen months of clashes between police and demonstrators, angered at the repeated killings of Black Americans by law enforcement officers across the country.
The protesters involved in Wednesday's clashes had earlier attended a 300-strong peaceful rally in a downtown park hosted by a coalition of anti-capitalist groups featuring lectures, music and slogans including "The Vote is Over. The Fight Goes On."
Rally organizer Evan Burchfield told AFP the city had been using the police as a "tool of political repression" for years and that "nothing is actually going to change" if Joe Biden is elected.
Another group of protesters who had gathered by Portland's river Wednesday vowed to "protect the results" of Tuesday's close-run election and held banners proclaiming "Count Every Vote."
"We want Trump out of office, that's the main focus," one rally leader told the crowd, to loud cheers.
Several of the demonstrators were openly carrying firearms, including rifles, and one anti-racism and anti-imperialism banner showed an image of an assault rifle, with the slogan "We Don't Want Biden. We Want Revenge."