Thousands of protesters angry over Donald Trump's election win took to the streets for a second straight night on Thursday, with at least one demonstration degenerating into a riot against the tycoon turned president-elect.

Accusing Trump of racism, sexism and xenophobia, protesters from New York to Los Angeles blocked traffic and chanted slogans like "Not my president" and "We reject the president-elect."

The worst violence was in the northwestern city of Portland, where protesters hurled projectiles at officers, vandalized businesses, smashed car windows and attacked drivers.

Police said they were treating the protests as a "riot" due to what they said was "extensive criminal and dangerous behavior."

In his first comments on the unrest, Trump blamed the media.