The protests have become a polarizing issue ahead of the November 3 presidential election
The governor of Minnesota declared a state of peacetime emergency in the city of Minneapolis after violent protests erupted on Wednesday night following the death of a Black homicide suspect who police say shot himself.
The city has been the centre of protests following the death of George Floyd, a 46-year-old African-American man, who died in May after a police officer knelt on his neck for nearly nine minutes.
Floyd's death and further violence against Black people have led to broader anti-racism protests and demonstrations against police brutality in cities across the United States.
Minneapolis Mayor Jacob Frey imposed a curfew following what he described as mass looting of businesses, destruction of property and unrest. Authorities also said there was misinformation spread in relation to the death of the suspect.
Video posted on social media, which could not be immediately verified by Reuters, showed shots being fired and ransacking of shops.
Minneapolis police posted a surveillance video of the shooting on Twitter, saying that the victim, a suspect in a homicide, committed suicide and that no weapons were fired by police.
The video shows a Black man shooting himself at the entrance of a building as a nearby group of people ran away and police approached the scene.
Minnesota governor Tim Walz declared a state of emergency in Minneapolis and said the National Guard would be deployed in the area.
"Dangerous, unlawful behavior will not be tolerated. The Minnesota National Guard and State Patrol are headed to Minneapolis to help restore order," Walz said in a statement.
The police shooting of a Black man, Jacob Blake, in the back in Kenosha, Wisconsin, on Sunday sparked three nights of unrest there that has included a wave of arson, widespread vandalism and a separate shooting that killed two people.
The protests have become a polarizing issue ahead of the November 3 presidential election, which Vice President Mike Pence and other Republicans described as a choice between "law and order" and lawlessness at their national convention on Wednesday.
"The hard truth is you won't be safe in Joe Biden's America," Pence told the crowd seated on a lawn at historic Fort McHenry in Baltimore in reference to the Democratic challenger to President Donald Trump.
Police in Portland, Oregon, on Wednesday declared a demonstration near a US immigration agency building as an "unlawful gathering", ordering the crowds to disperse. Police said they made 11 arrests in the city which has been the scene of weeks of anti-racism protests and unrest.
Violent protests also erupted in Oakland, California, resulting in the arrests of several people after multiple fires were set during the demonstrations, according to police.
Oakland police said on Twitter a fire was started at the Alameda Superior Court by people who protested in solidarity with Wisconsin demonstrators on Wednesday.
The National Basketball Association, protesting against racial injustice, postponed three playoff games scheduled for Wednesday after the Milwaukee Bucks boycotted Game 5 of their playoff series against Orlando Magic.
And tennis player Naomi Osaka pulled out of the semi-finals of a tennis tournament in Ohio on Wednesday in protests against the shooting of Blake.
Osaka, who has a Japanese mother and Haitian father and has been a vocal supporter of the "Black Lives Matter" movement, said in a social media post: "Before I am an athlete, I am a Black woman".