Police clashed with anti-racism protesters and pushed back members of the press in downtown Portland, Oregon into early Sunday morning.
More than 20 arrests were made; police declared a riot after they said rocks and cans were thrown at officers.
Social media postings showed police pushing protesters and photographers to the ground and jabbing them with batons as officers drove them out of an area near Portland’s federal courthouse.
Protesters burned a U.S. flag and clashed with police as they tried to arrest demonstrators.
The violence followed a relatively peaceful rally by the self-declared “Western chauvinist” Proud Boys group on Saturday.
Wearing black and yellow polo t-shirts and militarized body armor, with many brandishing weapons, Proud Boys members railed against Democratic leaders in Portland as protests over police violence and racism have rocked the city for months.
Proud Boys chairman, Enrique Tarrio: "But it isn't protest, they're burning down cities. What does that do for George Floyd." Anti-fascists and Black Lives Matter groups held a counter-protest two miles to the south.
Ahead of the rally, Oregon Governor Kate Brown declared a weekend state of emergency.
The Proud Group forecast the rally would draw a crowd of at least 10,000.
Police said fewer than 1,000 showed up.