Seattle police converged on the city’s “occupied” protest zone after mayor Jenny Durkan issued an executive order for protesters to vacate the area.
People have occupied several blocks around a park and the Seattle Police Department’s East Precinct for about two weeks after police abandoned the building following standoffs and clashes with protesters calling for racial justice and an end to police brutality.
Police said the move on Wednesday is designed to protect the public.
Protesters in the Capitol Hill neighbourhood responded with chants and calls to leave them alone.
“Since demonstrations at the East Precinct area began on June 8, two teenagers have been killed and three people have been seriously wounded in late-night shootings,” Seattle police said on Twitter.
“Police have also documented robberies, assaults, and other violent crimes.
“Because suspects in recent shootings may still be in the area, and because numerous people in the area are in possession of firearms,” they said.
Officers will be equipped with additional protective gear as they attempt to clear the streets.
KUOW radio reported that by 5.30am, police had made at least 10 arrests.
Cement barricades that remained in front of the Seattle Police Department East Precinct building Tuesday were fortified by protesters with chunks of concrete and tarps.
There have been increasing calls by critics, including President Donald Trump, to remove protesters from the Capitol Hill Occupied Protest area east of downtown following the fatal shooting Monday of a 16-year-old boy and the June 20 killing of a 19-year-old man.
Protesters say they should not be blamed for the violence in the area.
People continued to add artwork, flowers and candles at a memorial for the 16-year-old on Tuesday.
Police chief Carmen Best has said the shootings are obscuring the message of racial justice promoted by protesters.
Television images showed no immediate signs of clashes between the police, many dressed in riot gear, and dozens of protesters at the Capitol Hill Occupied Protest zone that was set up near downtown following the police killing of George Floyd in Minneapolis.
Police moved in to the zone known as Chop at about 5am and a loud bang was heard at about 6.15am followed by a cloud of smoke.
KUOW radio reported police had made at least 10 arrests by 5.30am.