A woman raises her arms as riot police fire tear gas during a protest outside the 5th Police Precinct in Minneapolis, the United States, on May 30, 2020. (Photo by Angus Alexander/Xinhua)

Some 5,000 U.S. National Guard troops were deployed to patrol a dozen major U.S. states on Sunday amid ongoing George Floyd protests against racism and police violence, which have sent shock waves through the country.

The national guard soldiers would assist law enforcement officers in the states who are in charge of security in the face of riots, and "thousands more stand ready if needed," Chief of the National Guard Bureau Gen. Joseph Lengyel tweeted.

Demonstrators in at least 30 cities across 16 states in the United States have been protesting against police violence and racism since May 25, when George Floyd, an unarmed 46-year-old African American male, died at the hands of a white police officer in the city of Minneapolis, Minnesota.

A protestor wears a face mask emblazoned with "I Can't Breathe" outside the 5th Police Precinct in Minneapolis, the United States, on May 30, 2020. (Photo by Angus Alexander/Xinhua)

On Saturday evening, U.S. Army Secretary Ryan McCarthy directed the activation of Washington D.C. National Guard in response to the U.S. Park Police asking for assistance with the protests, Commanding General William Walker said in a statement.

"Crossing State lines to incite violence is a FEDERAL CRIME!" U.S. President Donald Trump tweeted on Saturday afternoon. "Liberal Governors and Mayors must get MUCH tougher or the Federal Government will step in and do what has to be done, and that includes using the unlimited power of our Military and many arrests."

Minnesota National Guard troops stand watch on Lake Street in Minneapolis, Minnesota, the United States, May 30, 2020. (Photo by Ben Hovland/Xinhua)

"There's been an uptick in tension and hatred and division since (Trump) came along," New York City Mayor Bill de Blasio said in a news conference on Saturday. "It's just a fact."

Some political pundits said they believe that the widespread protests had more to do with Americans' frustration over the Trump administration's politically divisive tactics than the actual murder of Floyd by a white police officer.

Many said the Trump administration's policies to divide the United States were on display throughout the country this weekend.

They accused Trump of repeatedly and openly condoning or supporting hate groups during his presidency, which was unprecedented for a U.S. president. For example, in 2017, Trump said there were "very fine people on both sides" of clashes at a white supremacist rally in Charlottesville, Virginia.

Zip ties are seen on police officers on a street of lower Manhattan near Foley Square in New York, the United States, May 29, 2020. (Xinhua/Wang Ying)

Atlanta Mayor Keisha Lance Bottoms said Trump, who has often urged police to use tough tactics, was not helping matters.

"We are beyond a tipping point in this country, and his rhetoric only enflames that," she said on CBS.

As many as 25 cities have imposed curfews while at least eight states and Washington D.C. have called on the National Guard to help respond to protests as of Saturday, said a CNN report.

Nearly 1,400 people have been arrested during the protests in 17 cities since Thursday, according to an AP tally, adding that the actual number is likely higher as protests continued over the weekend.

Police arrest a protester in New York, the United States, May 29, 2020. (Photo by Michael Nagle/Xinhua)

A number of popular landmarks of the U.S. capital around the National Mall in central Washington D.C. were defaced with graffiti on Sunday.

In Washington D.C. on Saturday, protesters gathered outside the White House for the second straight day, chanting "hands up, don't shoot" and "I can't breathe."

Los Angeles Mayor Eric Garcetti on Saturday extended a curfew, which was initially applied only to downtown, to the whole city, requiring everyone within the City of Los Angeles to stay indoors from 8 p.m. to 5:30 a.m. Sunday.

"The vast majority of people taking to the streets are doing it peacefully, powerfully, and with reverence for the sacred cause they're fighting for. This curfew is in place to protect their safety -- and the safety of all who live and work in our city," Garcetti said in a statement.