People dressed in black and with their faces covered broke windows and the glass door at the Democratic Party of Oregon business office in Portland, spray-painting an anarchist symbol over the party sign, video posted on social media showed.

"We don't want Biden. We want revenge for police murders, imperialist wars, and fascist massacres," read a banner they marched under.

The new Democrat president was sworn in on Wednesday, urging unity and restoration after Republican Donald Trump's divisive tenure.

Portland has been the scene of unrest for months, with civil rights, anarchist and anti-fascist protesters scuffling with police and occasionally with right-wing militias and Trump supporters.

The protests began in the summer as part of nationwide demonstrations against racism and police brutality following the death of George Floyd, a Black man who died in Minneapolis in May after police pinned his neck to the ground for nearly nine minutes.