By Shaun TANDON with Julia BENARROUS in Houston

WASHINGTON, June 3 (AFP) — Leaders across the United States sought ways Tuesday to stem mounting unrest over police racism, from extending curfews to engaging protesters, as President Donald Trump dismissed fierce criticism for deploying force to break up a peaceful rally.

Eight days after George Floyd, an unarmed African-American man, suffocated beneath the knee of a white police officer in Minneapolis, once-in-a-generation demonstrations against systemic racism and police brutality in America show few signs of slowing down, despite Trump's threats of a military crackdown.

In Floyd's hometown of Houston, tens of thousands gathered to pay tribute to him Tuesday.

"Today is not about City Hall, it's about George Floyd's family, we want them to know that George did not die in vain," mayor Sylvester Turner told an estimated 60,000 people in the Texas city where Floyd grew up and is set to be buried.

Protests have been held in cities across the country, mostly peaceful but many descending into mayhem as night falls, with both activists and officials blaming rabble-rousers, and thousands arrested.

New York on Tuesday prolonged its first curfew since World War II for the full week, while the military could be seen in the streets of the capital Washington as peaceful protesters marched once again towards the White House.

Floyd died after he was pinned for nearly nine minutes under the knee of a white police officer, Derek Chauvin, who ignored his haunting pleas for life. 

"We must take this moment to change it all," Minnesota's Lieutenant Governor Penny Flanagan said of structural discrimination. 

She told reporters the state was launching a civil rights investigation of the Minneapolis Police Department, examining possible violations going back 10 years.

In Los Angeles, one of dozens of cities hit by unrest, police officers and Mayor Eric Garcetti dropped to their knees in a symbolic act of solidarity as they met marchers led by African-American Christian groups.

"A black face should not be a sentenced to die, nor to be homeless, nor to be sick, nor to be underemployed, nor to be under-educated," Garcetti told them, inviting the leaders into City Hall for a discussion about the issues.

Former president George W. Bush called on the US to examine its "tragic failures" and to "listen to the voices of so many who are hurting and grieving."

'People liked my walk'

In Washington, thousands returned to the streets Tuesday for a peaceful "Black Lives Matter" march.

Three hours after the 7:00 pm curfew protesters could be heard chanting and helicopters hovering above the streets near the White House, but the situation still appeared to be calm.

"I'm just tired, essentially, of being scared of police, of not getting justice," said Jada Wallace, an 18-year-old protester outside the White House earlier who said she was ready to risk arrest.

In the same place on Monday, federal police had abruptly opened tear gas and fired rubber bullets to break up a non-violent protest, clearing a path for Trump to stroll outside for a photo-op at a historic church damaged the previous night.

The move was loudly condemned by religious leaders, the president's political rivals, and onlookers around the country.

But Trump, who has rejected the traditional presidential role of healer, voiced glee on Twitter over the response in Washington and accused the leadership of New York — led by the rival Democratic Party — of succumbing to "Lowlife & Scum."

"Overwhelming force. Domination," he wrote, adding: "Washington, D.C., was the safest place on earth last night!"

He pushed back against the criticism later on Twitter, writing: "You got it wrong! If the protesters were so peaceful, why did they light the Church on fire the night before? People liked my walk."

Joe Biden, Trump's presumptive Democratic rival in November elections, denounced the crackdown on peaceful protesters as an abuse of power and promised, if elected, to tackle the "systemic racism" in the country.

"Donald Trump has turned this country into a battlefield driven by old resentments and fresh fears," Biden said in a speech in Philadelphia, also hit by violence.

The United States also faced unusual, if polite, criticism from some international allies.

German Foreign Minister Heiko Maas called the anti-racism protests "understandable and more than legitimate."

Germany, Britain and Australia voiced concern about the safety of the media after a number of journalists were roughed up by police or occasionally by rioters.

Curfew extended in New York

New York, the fabled "City that Never Sleeps" that had just been emerging from weeks under lockdown over the coronavirus, extended a curfew through Sunday that will start each night at 8.00 pm.

"We will take steps immediately to make sure there will be peace and order," Mayor Bill de Blasio, who has a fraught relationship with the police, said with visible anger.

The curfew began Monday at 11.00 pm — too late to spare New York widespread looting, with rioters smashing storefronts on posh Fifth Avenue. 

Several thousand took to the streets Tuesday in Manhattan, kneeling and shouting "George Floyd, George Floyd."

Protester Nat Hooper, 27, an African-American bookseller, called demonstrations "our civic duty" and hoped that Trump would be voted out in November.

Thousands continued to march in the city after Tuesday's curfew. 

Minneapolis was relatively calm but violence spread elsewhere. 

A Las Vegas officer was in "grave condition" Tuesday after being shot during protests overnight. An armed Hispanic man was shot and killed by police after raising his gun in a separate, nearby incident.

Four officers were also shot overnight in St. Louis. None of the injuries was life-threatening.

But one retired St Louis police captain was shot dead early Tuesday outside a ransacked store.

Trump tweeted that David Dorn, who was black, was "viciously shot and killed by despicable looters."