Social media videos showed chaotic scenes of people running and screaming amid a volley of gunfire and others tending to gunshot wounds.

The bloodshed followed a night of skirmishes that had appeared to turn calm, settling down after police fired tear gas and rubber bullets at protesters who defied a curfew.

The shooting that broke out shortly before midnight killed two people and wounded a third who was expected to survive, the Kenosha Police Department said in a statement.

Crowds chased a man running down the street with a rifle after they believed he had shot another man. One pursuer took a flying kick at him after he fell to the ground, and another tried to grab his weapon. He appeared to be shot at close range and fell to the ground.

Another video showed a man who appeared to be shot in the head as people nearby tried to treat him, and another showed a man with a severe arm wound.

Kenosha has been rocked by protests since Sunday, when police shot Jacob Blake in the back at close range as he walked away from two officers and opened his car door, according to a bystander video that went viral. Three of his young sons were in the car, witnesses said.

Blake, 29, was hit by four of the seven shots fired and left paralysed and "fighting for his life," his family and lawyers said on Tuesday, hours before the latest round of civil unrest broke out in the lakefront town between Milwaukee and Chicago.

Anti-racism protesters also clashed with police in Portland, Oregon, and Louisville, Kentucky, on Tuesday night, part of a wave of national protests that have continued since the May 25 death of African-American man George Floyd in Minneapolis, where he was pinned to the street under the knee of a white police officer.

Police arrested more than 60 people in a protest march in Louisville, Kentucky, organised for Breonna Taylor, a black woman killed in March by police officers who burst into her apartment.

The Kenosha protests have drawn self-styled militias, patrolling the streets with rifles. Usually white men, they have weapons slung over their shoulders or at the ready while standing guard outside businesses to protect them from looters or arsonists.'

"They're like a vigilante group," Kenosha County Sheriff David Beth told the Journal Sentinel, though he said he was unsure if the man at the centre of the outburst was linked to such a group.

Beth predicted the main suspect would be caught, telling the newspaper: "I feel very confident we'll have him in a very short time."

Australian Associated Press