'Black lives matter'

Several thousand people gathered at Freedom Plaza near the White House ahead of the rally shouting "No justice, no peace!" which had become a signature chant at nationwide demonstrations.

Both black and white people were in the crowd and many were holding banners proclaiming, "Stop racist police" and "Black lives matter."

Sponsored by civil rights groups, the march was scheduled to end at the Capitol where speakers would outline a legislative agenda in relation to police killings.

Lasting impact of final words

It's the latest in a series of protests held following several killings at the hands of the police, including the deaths of Michael Brown and Eric Garner.

Brown, 18, was shot dead by white police officer Darren Wilson in the town of Ferguson, Missouri, in August. A grand jury decision last month not to indict Wilson over the killing sparked several protests, some of which became violent.

The ruling was shortly followed by a further grand jury decision not to charge white police officer Daniel Pantaleo who was implicated in the so-called "chokehold" death in July of 43-year-old Eric Garner in Staten Island, New York.

Garner, a father-of-six, was pinned down by police officers after being arrested on suspicion of illegally selling cigarettes on the streets.

It's reported Garner's final words as he was tackled to the ground by officers were "I can't breathe." The words have become a rallying call at protests against police violence across the United States.

The incident went viral after the passer-by who filmed his arrest released the mobile phone footage on the Internet.

Unrest over killings

In a separate case, a prosecutor announced last week that a grand jury would decide whether to charge the officer who shot dead unarmed 28-year-old Akai Gurley in Brooklyn in November.

Elsewhere, there was public outrage about the death, also in November, of 12-year-old Tamir Rice. The boy was shot dead by Cleveland police in Ohio City as he brandished a toy gun.

Their respective families were expected to join the "Justice For All March" in the heart of the US capital.

The relatives of another unarmed black man, Trayvon Martin, who was shot dead by a neighborhood watch official in 2012, were also reported to be attending the rally.

As protesters descended on the Capitol in Washington, other groups including Ferguson Action were expected to hold similar "Day of Resistance" rallies across the United States.

A march was also planned in New York City against what was described by activists as "police brutality."

lw/sms (AFP, Reuters)