Federal authorities have forced demonstrators away from a plaza near a federal building as duelling demonstrations in Portland by right-wing and left-wing protesters turned violent.
The area includes county and federal buildings and has been the site of numerous recent protests.
Department of Homeland Security officers moved through the plaza across from an 18-storey federal building. A federal courthouse is also near that area.
The demonstration began about noon local time on Saturday near the Multnomah County Justice Center in Oregon's biggest city, local media outlets reported.
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Demonstrators hurled rocks and other items at each other and got into fights. Images showed what appeared to be hundreds of people involved, many of them wearing helmets and carrying makeshift shields. No arrests were reported.
The justice centre in recent weeks has been the target of left-wing protesters mostly operating at night, when they frequently get into clashes with police.
Saturday afternoon's demonstrations spread to other areas as crowds marched.
Right-wing groups had announced a rally near the justice centre on Saturday afternoon that quickly drew counter-demonstrators.
The protesters included the Proud Boys right-wing group and left-wing protest groups Democratic Socialists of America and Popular Mobilization, local media The Oregonian/OregonLive reported.
Violent demonstrations have gripped in Portland for months, following the police killing of George Floyd in Minneapolis police custody.
The Saturday afternoon clashes followed pre-dawn clashes between police and about 200 left-wing protesters outside a different police precinct.
Earlier in the morning, President Donald Trump had tweeted: "Another bad night of Rioting in Portland, Oregon,"
