Hundreds of mourners joined an emotional memorial service in Minneapolis Thursday for George Floyd, the black man killed by police last week, as civil rights leader Al Sharpton vowed mass protests will continue until "we change the whole system of justice."

Largely peaceful demonstrations took place later in cities from coast to coast. In New York, thousands marched over Brooklyn Bridge, while in Washington and Los Angeles curfews were lifted and crowds reduced.

People are arrested in Hollywood, California on June 1, 2020 as police impose a curfew People are arrested in Hollywood, California on June 1, 2020 as police impose a curfew Photo: AFP / Robyn Beck

In Minneapolis, Floyd's attorney told mourners he would find justice for the 46-year-old, who died during a May 25 arrest when a white police officer knelt on his neck for nearly nine minutes.

"It was not the coronavirus pandemic that killed George Floyd," said Benjamin Crump, who is representing Floyd's family. "It was that other pandemic. The pandemic of racism and discrimination."

A broken glass at a Capitol One bank in New York A broken glass at a Capitol One bank in New York Photo: AFP / Johannes EISELE

The crowd stood in silence for eight minutes and 46 seconds -- the same length of time that officer Derek Chauvin spent with his knee on Floyd's neck, a scene captured on video.

Floyd's death has reignited long-felt anger over police killings of African-Americans and unleashed a nationwide wave of civil unrest unlike any seen in the US since Martin Luther King Jr's 1968 assassination.

George Floyd Mural A mural in Berlin honors George Floyd, a black man whose killing in Minneapolis by a white police officer unleashed protests across the United States Photo: AFP / David GANNON

With marches for racial justice stretching beyond the US and around the world, Sharpton said Floyd's death would not be in vain.

"It's time for us to stand up in George's name and say get your knee off our necks," said the 65-year-old Baptist minister.

US President Donald Trump holds up a bible in front of St John's Episcopal church after walking across Lafayette Park from the White House in Washington, DC on June 1, 2020 President Donald Trump holds up a bible in front of St John's Episcopal church after walking across Lafayette Park from the White House in Washington, D.C. on June 1, 2020. Photo: AFP / Brendan Smialowski

"You changed the world, George," he said. "We're going to keep fighting, George."

"We're going to keep going until we change the whole system of justice."

Protesters hold their hands up and try to steady themselves as a military helicopter flies low over a protest in Washington Protesters hold their hands up and try to steady themselves as a military helicopter flies low over a protest in Washington Photo: AFP / ROBERTO SCHMIDT

Members of Floyd's family were among several hundred people attending the North Central University service.

Minneapolis police chief Medaria Arradondo dropped to a knee as the hearse bearing Floyd's remains arrived for the service.

Protestors are tear-gassed as the police disperse them near the White House on June 1, 2020 Protestors are tear-gassed as the police disperse them near the White House on June 1, 2020 Photo: AFP / ROBERTO SCHMIDT

Democratic presidential candidate Joe Biden speaks about the unrest across the country from Philadelphia City Hall Democratic presidential candidate Joe Biden speaks about the unrest across the country from Philadelphia City Hall Photo: AFP / JIM WATSON

A vigil for Floyd was also held in New York and was attended by thousands of people, including Floyd's brother, Terrence.

"White Silence is Violence," a sign read. "Make America Not Embarrassing Again," read another.

Protestors hold up placards during a Black Lives Matter demonstration in New York over the death of George Floyd Protestors hold up placards during a Black Lives Matter demonstration in New York over the death of George Floyd Photo: AFP / Angela Weiss

Arrests were reported in Manhattan after the 8:00 pm curfew passed.

Upstate in Buffalo, two police officers were suspended without pay after a video showed them pushing over an elderly protester who fell and suffered a head injury.

The owner and manager of a photography store assess the damage after looting The owner and manager of a photography store assess the damage after looting Photo: AFPTV / Eleonore SENS

Reporting the suspension on Twitter, city mayor Byron Brown said he and the police commissioner were "deeply disturbed" by the video.

An earlier police statement said the man, who appeared unconscious and bled heavily from one ear, "tripped and fell."

The owner and manager of a photography store assess the damage after looting The owner and manager of a photography store assess the damage after looting Photo: AFPTV / Eleonore SENS

"This incident is wholly unjustified and utterly disgraceful," New York governor Andrew Cuomo tweeted.

"Police Officers must enforce - NOT ABUSE - the law."

A Republican senator, Lisa Murkowski of Alaska, broke ranks with her party meanwhile and revealed she was "struggling" with whether to support President Donald Trump's re-election.

Murkowski said her move was prompted by remarks from Trump's former defense secretary James Mattis, who a day earlier delivered a biting assessment of a president who "tries to divide us."

"I thought General Mattis's words were true and honest and necessary and overdue," Murkowski told reporters.

Her comments mark a major break with Trump within the Republican camp, which has largely held together through various crises including his impeachment and current threat to use military force against protests.

While condemning Floyd's death, Trump has adopted a tough stance towards the protesters, saying they include many "bad people" and calling on governors to "dominate the streets."

US civil rights groups filed a case Thursday suing Trump, after security forces fired pepper balls and smoke bombs to clear peaceful demonstrators outside the White House before the president walked to a church for a photo op earlier this week.

Low-flying choppers were also used in an apparent show of force above protesters in Washington, DC on Monday night.

Trump tweeted: "The problem is not the very talented, low-flying helicopter pilots wanting to save our city, the problem is the arsonists, looters, criminals, and anarchists, wanting to destroy it (and our Country)!"

His re-election campaign accused Twitter of censorship after its post of video paying tribute to Floyd, narrated by a speech Trump gave on the killing, was removed following a copyright complaint.

Democratic Congressman John Lewis, who marched with Martin Luther King Jr to fight segregation, echoed Sharpton's hope that Floyd's death could pave the way for "greater change."

The 80-year-old civil rights icon told "CBS This Morning" that the current protests felt "so much more massive and all-inclusive." He also condemned Trump's threat to use military force against demonstrators.

Some of the protests were marred by rioting and looting in the early days, but they have been mostly peaceful since then.

Bail was set at $1 million each.

The fourth policeman, Chauvin, has been charged with second-degree murder and appeared before a judge last week.