Police arrested eight people in Seattle after late night demonstrations and marches in the city on U.S. Election Day, police said.

There were no immediate reports of injuries or that the protests were linked to the U.S. election, but some demonstrators carried "Black Lives Matter" banners, Q13 Fox Seattle television reported.

The Seattle Police Department said the arrested people included one who put nails in a road and another who drove over a barricade and into a police bike lane.

Two marches were held through the city's South Lake Union and Capitol Hill areas, with the police cautioning people travelling to those places.

The police said marchers had moved traffic barricades into the roadway, with the police initially issuing a public safety warning and then a dispersal order to a group of protesters at Broadway.

"Eight arrests this evening for pedestrian interference, obstruction, assault on an officer, reckless driving, and criminal mischief", Seattle Police said on Twitter.

In recent months, Seattle, like elsewhere in the United States, has seen protests against racism and police brutality following the death in May of George Floyd, an African-American who died after a Minneapolis police officer knelt on his neck for nearly nine minutes. Protesters have previously called for police reforms.

Election day unfolded smoothly across much of the United States in a mostly calm show of political determination and civic duty amid the coronavirus pandemic despite fears of disruption.