Wisconsin city centre burns amid protests

Arsonists have torched much of the black business district during a second night of unrest in Kenosha, Wisconsin, triggered by the wounding of a black man shot in the back by police as his three young sons looked on.

Police in riot gear clashed with protesters as they defied a dusk-to-dawn curfew on Monday night and Tuesday morning, blocks away from where police gunned down Jacob Blake on Sunday.

Blake, 29, survived the shooting, which was captured on video, and was in stable condition following surgery, his father said.

Blake had been attempting to break up a fight between two women and was shot in front of his three young sons, civil rights lawyer Ben Crump said.

Video shows Blake walking toward the driver's side door of his car, away from two officers who were pointing guns to his back. After he opens the door, seven shots ring out with one of the officers tugging at his shirt. It remains unknown what the officers may have seen inside Blake's car.

The incident unleashed outrage in the lakefront city of Kenosha, located north of Chicago and south of Milwaukee.

The shooting occurred three months after the death of George Floyd, a black man in Minneapolis who was pinned to the street under the knee of a white police officer, sparking nationwide protests against police brutality and racism.

Unrest flared again elsewhere in the US with overnight clashes reported in Portland, Seattle and Minneapolis.

Portland, Oregon, has been the scene of weeks of protests following Floyd's death that have sometimes turned violent. Police there once again declared a riot late on Monday and arrested demonstrators after fires were lit at the offices of a police union.

Seattle police said demonstrators set multiple buildings on fire, resulting in at least one arrest and one officer injured.

In Minneapolis, protesters including one man armed with a gun stopped an armoured police vehicle in the street until officers cleared the way with tear gas.

Black Lives Matter activists are demanding the immediate firing or arrest of the Kenosha officers, who have been placed on administrative leave.

Hours into the curfew, the mostly peaceful demonstration turned violent with some protesters setting off fireworks in front of police. Commercial and government buildings were set ablaze, along with vehicles in car dealership lots.

Local police who had support from National Guard troops fired tear gas, rubber bullets and smoke bombs to disperse the crowd, which grew to several hundred, according to protester Porche Bennett, 31, of Kenosha.

Fires destroyed much of the black business district, Bennett said, adding that the instigators she saw were white.

"It's people from out of town doing this. We've been shopping there since we were kids and they set it on fire," Bennett said.

Social media images showed both white and black agitators. Black men swinging baseball bats broke traffic signals and street lamps. White and black men with bats bashed in the headlights and windshields of a row of cars.

One white man riding a skateboard doused a government truck with an accelerant and set it on fire. Heavily armed white civilians stood guard in front of one business to protect it from vandals.

At least one man was injured, shown on social media bleeding from the head as civilians administered aid.