Thousands of people have protested in Washington DC against the recent killings of unarmed black people by police.
Relatives of Michael Brown, shot dead in the Missouri town of Ferguson, and Eric Garner, who died being restrained in New York, were among them.
Both died after encountering police, but grand juries decided not to bring charges, sparking anger and unrest.
Another demonstration in New York also drew thousands despite chilly weather.
Speakers at the Capitol called for changes to US legislation.
Lesley McSpadden, mother of Michael Brown, told the crowd: “What a sea of people. If they don’t see this and make a change, then I don’t know what we got to do. Thank you for having my back.”
The mood in Washington DC was described as calm but defiant, with a large number of police on standby.
Earlier in the day, a small group of protesters from Missouri disrupted the schedule by taking to the stage at the starting-point, on Freedom Plaza, and blowing a bullhorn.
They complained that the protest, which was organized by long-established civil rights groups, was staid and ineffective.
Michael Brown, 18, was shot dead on August 9 during an altercation with a white police officer in Ferguson, Missouri.
Eric Garner, 43, died while being held down by a white police officer on July 17.
He had been challenged over the alleged sale of loose cigarettes on a street in Staten Island, New York.
The event was caught on camera and his dying plea of “I can’t breathe” has become a slogan of the protesters. It echoes the adoption of “Hands up! Don’t Shoot!” – a Ferguson refrain alleging that Michael Brown was surrendering to police when the fatal shots were fired.
Relatives of three other black people killed in controversial shootings were also expected to attend the march, according to the National Action Network:
Akai Gurley, 28, was shot dead by New York police on November 20
Tamir Rice, 12, was shot dead in a Cleveland, Ohio, park on November 22 while carrying a pellet gun
Trayvon Martin, 17, was shot dead on February 26, 2012, by a neighborhood watch volunteer in Sanford, Florida
Marchers crowded Pennsylvania Avenue for the walk from Freedom Plaza to the Capitol, but the actual numbers were not immediately clear.
Some in the crowd, which was made up of both black and white people, held banners saying: “Stop racist police”, “I can’t breathe”, and “President Obama seize this moment. The ancestors are watching.”
The Rev Al Sharpton, a leading civil rights advocate, called for “legislative action that will shift things both on the books and in the streets”.
A new US grand jury will decide whether to prosecute a NYPD officer over the fatal shooting of unarmed black man Akai Gurley in Brooklyn.
Akai Gurley was shot in the chest after he entered the stairwell of his apartment building last month.
The decision comes days after a grand jury opted against charging a New York policeman in the chokehold death of another unarmed black man, Eric Garner.
The decision has sparked protests across the country.
The US was already facing race-related unrest over the decision not to indict a white police officer who had shot dead a young black man, Michael Brown, in Ferguson, Missouri.
In New York City on December, protesters briefly laid down in Macy’s flagship store, at Grand Central Terminal and at an Apple store.
Hundreds streamed along Fifth Avenue and other parts of Manhattan, with banners and chants of “Black lives matter” and “I can’t breathe” – a reference to the words of Eric Garner as he was being restrained by a white police officer.
Protests were also held in other US cities including Chicago, Washington, Denver, and Boston.
Meanwhile, a memorial service was held for 28-year-old Akai Gurley in New York ahead of his funeral on December 6.
At an earlier news conference, his mother tearfully demanded justice for her son.
Speaking alongside her, Kevin Powell, president of the advocacy group BK Nation, called the shooting part of a “series of modern-day lynchings”.
In announcing the grand jury – a body that determines whether to bring criminal charges – Brooklyn’s District Attorney Ken Thompson said it was important to conduct a full and fair investigation.
Police say Akai Gurley and his girlfriend had opened a door into the unlit stairway and an inexperienced officer on a routine patrol fired his gun.
New York Police Commissioner William Bratton called the shooting an accident. However, the medical examiner has ruled that the death is a homicide.
Civil rights leader the Reverend Al Sharpton had initially planned to speak at Akai Gurley’s memorial service but later said he would pay his respects without making an address.
UN human rights experts earlier expressed “legitimate concerns” about grand juries failing to charge the two policemen involved in the deaths of Eric Garner and Michael Brown.
In a statement, UN Special Rapporteur on minority issues, Rita Izsak, said it was part of a broader “pattern of impunity” concerning minority victims.
Following the outcry over the Garner case, New York Mayor Bill de Blasio ordered the city’s 22,000-strong police force to be retrained in how to better communicate and remain calm when making arrests. They will also be fitted with body cameras.
Activists have called for another march in Washington on December 13, followed by a summit on civil rights.