Tens of thousands of peaceful protesters rallied for racial justice in cities across the United States following the death of African American George Floyd at the hands of police.

Protests took place from New York to Los Angeles but Washington was at the epicenter, as thousands of people -- black, white and brown -- flooded downtown streets surrounding the White House, which was barricaded with black metal fencing.

"This fight has been happening for many, many decades, hundreds of years, and at this point it's time for a change," said Washington native Christine Montgomery.

"I'm here so my son is not the next hashtag that is circulating worldwide," she added, indicating her 10-year-old child standing next to her.

On a sunny but oppressively hot day, many people wore masks because of the coronavirus pandemic.

Volunteers gave out water, hand sanitizer and other supplies as the area took on a block party vibe, with music, mural painting, food trucks, and vendors selling Black Lives Matter T-shirts.

Helicopters circled overhead as some protesters danced -- but the pain which drove many in to the streets was never far below the surface, as others yelled "This ain't no party!"

Military personnel as well as police watched over the gathering. But there appeared to be fewer than on previous days, and some gave the protesters small smiles and waves as they marched by.

On the National Mall, fencing and uniformed guards blocked protesters from the steps of the Lincoln Memorial where civil rights icon Martin Luther King Jr famously delivered his "I have a dream" speech in 1963.

The protests were ignited by videos of a police officer kneeling on Floyd's neck for almost nine minutes as he pleaded for his life -- the latest unarmed black person to be killed by white law enforcement officers.

The officer, Derek Chauvin, has been charged with second-degree murder.

The rage since Floyd's death in Minneapolis on May 25 has exploded into the most serious civil unrest in America since King was assassinated in 1968.

Peaceful protests swelled Saturday in other US cities.

Tens of thousands rallied across New York City and Philadelphia, Chicago shut down the city's Lake Shore Drive to facilitate protests, and demonstrators marched in Los Angeles.

In San Francisco, thousands marched across the Golden Gate Bridge, briefly stopping traffic as they spilled into the driving lanes.

- 'I can't go in' -

But the demonstrations in Washington were the biggest since protests began in Minneapolis before spreading across the country and then abroad.

"Today, the pain is so raw it can be hard to keep faith," tweeted Democratic presidential hopeful Joe Biden.

A remembrance for Floyd was held Saturday in North Carolina, the state where he was born, following a memorial service in Minneapolis on Thursday.

Hundreds waited to view his coffin, some holding umbrellas against the hot sun. Some sobbed and many held cell phones high as a hearse arrived with the casket. 

Floyd's sisters LaTonya and Zsa-Zsa told reporters they would not go inside. 

"I can't go in, see him laying in a coffin, it would drive me crazy forever," said LaTonya through tears.

She expressed her pain at watching the footage of her brother's agonizing death. 

"Every time I look up I see him on the ground, face up, neck down, hollering please help me," she said, adding she wished the video could be taken down.

"I'll never hear his voice, I'll never hear his laughter, I'll never tell him again that I love him and likewise he'd tell me the same," said Zsa-Zsa.

- 'It's about time' -

Around the world, protesters echoed the rage of American demonstrators.

"It is time to burn down institutional racism," one speaker shouted through a megaphone at a hooting crowd of thousands outside the parliament building in London. 

Tens of thousands rallied in Australia and France, while in Tunis, hundreds chanted: "We want justice! We want to breathe!"

Back in Washington, many black protesters hailed the multiracial, multi-ethnic nature of the demonstrations, calling the change "invigorating."

Jackie Maddox, 59, who remembered her own parents marching in Washington for their rights decades ago, said she felt "relieved" that black people were no longer alone.

"It's about time that they are tired too," she said of other protesters -- though, she added, she hoped it would last.

The days of demonstrations in the US -- which have included outbreaks of looting and violence -- have seen new police abuses, some captured on camera.

Two policemen in Buffalo, New York were charged with felony assault Saturday after they were filmed shoving a 75-year-old protester who fell, hit his head and began bleeding, in one of the most widely shared videos fuelling outrage.

But there were some changes to policing as well. 

In Seattle, authorities announced a temporary ban on tear gas. A federal judge in Denver forbade the use of chemical agents and projectiles like rubber bullets against peaceful protesters. And in Dallas, police marched in solidarity with protesters.

The unrest has handed US President Donald Trump -- the target of many a biting protest sign and chant -- one of the greatest challenges of his tumultuous presidency.

While condemning Floyd's death, he has adopted a tough stance toward protesters, calling them "thugs" or "terrorists" and threatening a military crackdown.

"LAW & ORDER!" the president tweeted as evening fell Saturday, adding later that the crowd in DC was "much smaller" than anticipated.