People have defied curfews to mount a seventh night of protests in the United States, where outrage at the suffocation of a black man by police has spread from Minneapolis to more than 100 cities.
Five officers were shot and wounded in an escalation of tensions between police and crowds protesting the killing of George Floyd in police custody.
President Donald Trump taunted state governors for not embracing his proposal to send in the US military to quell unrest.
Demonstrators smashed windows and looted stores in New York City, including luxury retailers on Fifth Avenue, and set fire to a Los Angeles strip mall. Four officers were wounded in St. Louis and one in Las Vegas who was critically wounded, authorities said.
Democratic Governor Andrew Cuomo said he was outraged by the violence and looting in New York City on Monday, and that the city's mayor and police force "did not do their job last night." He said he believed Mayor Bill de Blasio underestimated the scope of the problem.
New York City Police Commissioner Dermot Shea said nearly 700 arrests were made,
Cuomo also said he may "displace" the mayor and order the National Guard into New York City. Mayor Bill de Blasio poured cold water on the idea and said when forces not trained to handle New York City crowds intervened, "still with loaded weapons and under stress, horrible things happen."
The head of the National Guard, General Joseph Lengyel, said violence had decreased across the United States on Monday night, even as protest activity was sustained or increased. He said no Guard members were injured overnight.
Lengyel said 18,000 Guard members were assisting local law enforcement in 29 states, a figure that was increasing.
The protests were triggered by the death of George Floyd, a 46-year-old African American who died after a white policeman pinned his neck under a knee for nearly nine minutes in Minneapolis on May 25.
Derek Chauvin, the 44-year-old Minneapolis police officer who planted his knee on Floyd's neck, has been charged with third-degree murder and second-degree manslaughter. Three other officers involved have not been charged.
Floyd's death has reignited the explosive issue of excessive police force, especially against African Americans, and raised tensions on the front lines where officers have faced off against sometimes hostile crowds.
Democratic presidential candidate Joe Biden pledged to push for policing reforms, including a ban on the use of chokeholds like the one that resulted in George Floyd's death.
In a televised address from Philadelphia's historic city hall, he also lashed out at Trump's handling of the nationwide crisis.
The former vice-president is trying to draw a sharp contrast with the current White House occupant - both by making concrete proposals for how law enforcement should operate and in suggesting that Trump's tone and attitude is ill-suited for the perilous moment in American history.
"I won't traffic in fear and division," Biden said. "I won't fan the flames of hate."
Trump has threatened to use the military to crack down on the unrest, now in a second week, and has derided local authorities, including US governors, for their response to the violent protests.
"New York was lost to the looters, thugs, Radical Left, and all others forms of Lowlife & Scum. The Governor refuses to accept my offer of a dominating National Guard. NYC was ripped to pieces," tweeted Trump, a Republican, in a reference to New York Democratic Governor Andrew Cuomo.
Trump has provided no evidence that leftists are behind the violence that has engulfed US cities.
- Reuters / BBC