Hundreds of people rallied and marched in New York and Boston to protest against the death of a Baltimore man who was critically injured in police custody.
More than 100 people were arrested in New York last night after police on a loudspeaker warned them they would be taken into custody if they marched in the street. Police said most arrests were for disorderly conduct.
Protesters first rallied in Manhattan's Union Square, where they chanted "No justice, no peace" and "Hands up, don't shoot" - a reference to the police killing of Michael Brown in Ferguson, Missouri, last year.
Then a group of protesters spilled into the street, disrupting traffic. Dozens of police officers moved in with plastic handcuffs and began making arrests while officers with batons pushed the crowd back on to the pavement.
In Boston, activists sparked by the death of Freddie Gray in Baltimore gathered in a park behind police headquarters in Roxbury and continued with a peaceful march to a park at Dudley Square.
Nikea Ramsey, whose brother Burrell Ramsey-White was shot and killed in an encounter with Boston police in 2012, said: "Me and my family, we stand with Baltimore. We stand with Ferguson. This is too much and it's getting out of hand."
Boston organisers said they want "amnesty" for the 300 protesters and rioters who have been arrested in Baltimore, as well as a lifting of the city curfew and state of emergency declaration.
Meanwhile in Philadelphia, protesters plan to conduct a "Philly is Baltimore" demonstration this afternoon at City Hall. They have drawn parallels between the death of a local man shot during a traffic stop and the April 19 death of Mr Gray in Baltimore.
The district attorney is not pressing charges in the December shooting death of Brandon Tate-Brown in Philadelphia, saying evidence indicates that he was reaching into his car for a loaded pistol. A lawsuit filed on Tuesday alleges that officers planted the gun.
Mr Gray's arrest was recorded on mobile phone videos by bystanders. His death has also led to protests, rioting and looting in Baltimore.
Baltimore police say they chased Mr Gray when he fled at the sight of an officer in a drug-infested neighbourhood. Officers pinned him to the pavement and then lifted him and took him, his legs dragging on the ground, to a police van.
Mr Gray, who asked repeatedly for medical help during the 30-minute journey to a police station, died a week later.
Police say he died of a "significant spinal injury". A lawyer for Mr Gray's family says his spine was "80% severed in the neck area".