Thousands of protesters across the US have defied curfews as President Donald Trump’s threat of using the military to quash violent protests and looting have been widely criticised.

As the US entered its seventh night of escalating protests, thousands of people marched through the streets of Brooklyn, shouting while cars drove alongside, some drivers honking in support.

TV images showed throngs looting luxury stores along Fifth Avenue in Manhattan, before the city’s 11pm curfew. Mayor Bill de Blasio said the curfew would be moved to 8pm on Tuesday.

In Hollywood, dozens of people were shown in television images looting a Rite-Aid drug store after the front door was smashed. Windows were shattered at a nearby Starbucks, a noodle shop and a kebab restaurant.

Elsewhere in Los Angeles, dozens of people were arrested and held against barricaded buildings with their hands zip-tied after breaking strict curfews.

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In Washington, military helicopters flew low over the protesting crowds, trying to disperse them. Some of the helicopters hovered immediately above demonstrators, hitting them with rotor wash and the deafening sound of engines.

Just before midnight in Buffalo in New York State, local media reported a four-wheel-drive ploughed through a group of law enforcement officers. Two officers were reportedly injured.

As a police helicopter flew low overhead, officers in armoured vehicles fired tear gas to disperse the crowd nearby. Several stores in the area were broken into, and people were seen leaving with goods.

Earlier on Tuesday (AEST), in an address from the White House Rose Garden, Mr Trump vowed to end what he labelled “domestic terrorism” as the violence spread to more cities.

“Mayors and governors must establish an overwhelming law enforcement presence until the violence has been quelled,” he said.

“If a city or state refuses to take the actions that are necessary to defend the life and property of their residents, then I will deploy the United States military and quickly solve the problem for them,” he said.

Mr Trump told the nation he would protect peaceful protesters, but there were many reports of protesters on the streets near Lafayette Park, which surrounds the White House, being shot with rubber bullets and dispersed with tear gas before his impromptu walk to a nearby church.

“We cannot allow the righteous cries of peaceful protesters to be drowned out by an angry mob. The biggest victims of the rioting are peace-loving citizens in our poorest communities and as their President I will fight to keep them safe. I will fight to protect you,” Mr Trump said minutes earlier.

He and his entourage left the White House and walked to St John’s Episcopal Church, which was damaged in looting the night before. They were accompanied by secret service and Homeland Security agents and officials, including US Attorney General William Barr.

After Mr Trump posed for photos holding a Bible outside the 1815 “Church of the Presidents” – where Abraham Lincoln prayed during the Civil War, Lyndon Johnson bowed his head the day after John F Kennedy’s assassination, and Bill Clinton once walked through a snowstorm, in flannel shirt and jeans, to attend services – his entourage quickly retreated behind the gates of the White House.

Mr Trump outside St John’s Church on Tuesday. Photo: AAP

Anti-police brutality marches and rallies, which have turned violent after dark, have erupted over the death of African American George Floyd, 46. He died in Minneapolis police custody a week ago after being pinned beneath a white officer’s knee for nearly nine minutes.

An autopsy ordered by Mr Floyd’s family and released on Monday found his death was a homicide by “mechanical asphyxiation”, meaning physical force interfered with his oxygen supply. The report says three officers contributed to Mr Floyd’s death.

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Mr Trump’s actions and words brought widespread anger from rival Democrats and church figures, after he described state governors as “weak”.

Critics accused him of stoking conflict and racial tension and New York’s governor criticised the use of force against demonstrators.

Washington governor Jay Inslee called Mr Trump “incapable”.

Mr Inslee said the President had “repeatedly proven he is incapable of governing and shown nothing but false bravado throughout the chaos that has accompanied his time in office”.

“Now he uses the most supreme power of the presidency in a desperate attempt to hide his timidity and vapidity. I pray no soldier and no civilian is injured or killed by this reckless fit,” he said.

Protesters confront police in Los Angeles. Photo: AAP

Oregon governor Kate Brown said she would not send National Guard troops to help quell protests in Portland because they weren’t needed and that “is exactly what President Trump wants”.

Ms Brown said she would send 100 state police from across Oregon to assist the city, and activate 50 Guard troops to work behind the scenes.

Derek Chauvin, the 44-year-old former Minneapolis police officer who kneeled on Mr Floyd, was arrested on third-degree murder and second-degree manslaughter charges and remains in custody.

Mr Trump heads out of the White House towards St John’s Church. Photo: AAP

Outrage over church visit

The bishop of the Episcopal Diocese of Washington, Reverend Mariann Budde has sharply criticised Mr Trump for his visit to St John’s Church.

She said she was “outraged” by the visit and noted that Mr Trump didn’t pray while there.

Nor did the President “acknowledge the agony and sacred worth of people of colour in our nation who rightfully demand an end to 400 years of systemic racism and white supremacy in our country”, Reverend Budde said in a statement on the diocese’s Twitter account.

Reverend Budde told CNN she heard from many people of faith “wondering what on Earth did we just witness?”.

“In no way do we support the President’s incendiary response to a wounded, grieving nation,” she said.

Celebrities weigh in on Trump’s church walk

Celebrities also spoke out on Tuesday.

Singer John Legend, a frequent critic of the President, accused Mr Trump of using law enforcement to clear peaceful protesters for a photograph.

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He tweeted: “#BunkerBoy Trump had to prove he could walk in broad daylight today so he sicced the police on peaceful protesters so he could stand there and awkwardly hold the Bible. Dear God. We need to end this nightmare of a presidency.”

Oscar-winning filmmaker Spike Lee, who calls Mr Trump “Agent Orange”, wrote on Instagram that the US was on the verge of a dictatorship.

Grammy-winning rapper Cardi B accused the President of threatening people and making protesters “more angry”.

Samuel L Jackson suggested Mr Trump had “declared war on the public,” admitting he fears “it’s about [to] get all kinds of f—ed up here!!”.

George Clooney penned an essay for The Daily Beast, saying America’s greatest pandemic was racism: “We need policymakers and politicians that reflect basic fairness to all of their citizens equally. Not leaders that stoke hatred and violence as if the idea of shooting looters could ever be anything less than a racial dog whistle.”

-with agencies