By Brad Brooks, Phil Stewart, Idrees Ali and Dietrich Knauth

LOS ANGELES (Reuters) -Hundreds of U.S. Marines arrived in the Los Angeles area on Tuesday under orders from President Donald Trump, ratcheting up tensions in America's second largest city, as California's governor warned "democracy is under assault."

Trump's extraordinary measures of sending National Guard and Marines to quell protests, which broke out in response to his immigration raids, fueled demonstrations for a fifth day in Los Angeles, and sparked protests in several other cities.

As Trump and Newsom traded fulminations, the city's mayor said the protests were limited to about five downtown streets, but declared a curfew for parts of the downtown area due to violence and looting.

Police arrested another 197 people on Tuesday - more than double the total number of arrests to date.

Democratic leaders have raised concerns over a national crisis in what has become the most intense flashpoint yet in the Trump administration's efforts to deport migrants living in the country illegally, and then crack down on opponents who take to the streets in protest.

"This brazen abuse of power by a sitting president inflamed a combustible situation, putting our people, our officers and even our National Guard at risk. That's when the downward spiral began," Newsom said in an a video address.

"He again chose escalation. He chose more force. He chose theatrics over public safety. ... Democracy is under assault."

Newsom, widely seen as preparing for a presidential run in 2028, has called the deployments an illegal waste of resources. He and the state sued Trump and the Defense Department on Monday, seeking to block the deployment of federal troops. Trump in turn has suggested Newsom should be arrested.

Trump, voted back into office last year largely for his promise to deport undocumented immigrants, used a speech honoring soldiers on Tuesday to defend his decision.

He told troops at the Army base in Fort Bragg, North Carolina: "Generations of Army heroes did not shed their blood on distant shores only to watch our country be destroyed by invasion and third-world lawlessness."

"What you're witnessing in California is a full-blown assault on peace, on public order and on national sovereignty, carried out by rioters bearing foreign flags," Trump said, adding his administration would "liberate Los Angeles."

Demonstrators have waved the flags of Mexico and other countries in solidarity for the migrants rounded in a series of intensifying raids.

Homeland Security said Monday its Immigration and Customs Enforcement division had arrested 2,000 immigration offenders per day recently, far above the 311 daily average in fiscal year 2024 under former President Joe Biden.

UNREST IN THE STREETS

Los Angeles Mayor Karen Bass on Tuesday announced a curfew for one square mile (2.5 square km) of downtown Los Angeles that will run from 8 p.m. to 6 a.m. locally (0300 to 1300 GMT) for several days.

With five minutes until the curfew took effect, hundreds of protesters faced police with their hands raised, chanting ""peaceful protest."

Even so, state and local officials have called Trump's response an extreme overreaction to mostly peaceful demonstrations.

Bass emphasized at a press conference the distinction between the majority of demonstrators protesting peacefully and a smaller number of agitators she blamed for violence and looting.

A curfew had been considered for several days but Bass said she decided to impose one after 23 business were looted on Monday night.

"When these peaceful rallies end, and the protesters head home, another element moves in: opportunists, who come in under the cover of a peaceful protest to ravage and destroy," Council member Ysabel Jurado, who represents the area, told reporters.

As the mayor and the council member spoke, police and protesters were engaged in skirmishes outside.

In what has become a daily ritual, police forced demonstrators away from the streets outside the Metropolitan Detention Center, where many detained migrants are held. Multiple groups of protesters snaked through downtown Los Angeles, monitored or followed by police armed with less lethal munitions.

Protests also took place in other cities including New York, Atlanta and Chicago, where demonstrators shouted at and scuffled with officers. Some protesters climbed onto the Picasso sculpture in Daley Plaza, while others chanted that ICE should be abolished.

Christina Berger, 39, said it was heartbreaking to hear about children who are afraid of being separated from their families due to immigration raids, adding, "I just want to give some hope to my friends and neighbors."

MARINES AT THE READY

About 700 Marines were in a staging area in the Seal Beach area about 30 miles (50 km) south of Los Angeles, awaiting deployment to specific locations, a U.S. official said.

A U.S. official said there were 2,100 National Guard troops in the Los Angeles area on Tuesday, more than half the 4,000 to be activated. The Marines and National Guard troops lack the authority to makes arrests and will be charged only with protecting federal property and personnel.

Even so, California Attorney General Rob Bonta told Reuters the state was concerned about allowing federal troops to protect personnel, saying there was a risk that could violate an 1878 law that generally forbids the U.S. military, including the National Guard, from taking part in civilian law enforcement.

"Protecting personnel likely means accompanying ICE agents into communities and neighborhoods, and protecting functions could mean protecting the ICE function of enforcing the immigration law," Bonta said.

U.S. Immigration and Customs Enforcement on Tuesday posted photos on X of National Guard troops accompanying ICE officers on an immigration raid. Trump administration officials have vowed to redouble the immigration raids in response to the street protests.

(Reporting by Jorge Garcia, Brad Brooks, Jane Ross and Arafat Barbakh in Los Angeles, Dietrich Knauth in New York, Idrees Ali, Phil Stewart and Trevor Hunnicutt in Washington and Tom Polansek in Chicago; Additional reporting by Sandy Hooper, Costas Pitas, Susan Heavey, Doina Chiacu, Ismail Shakil, Jasper Ward and Costas Pitas; Writing by Joseph Ax and Daniel Trotta; Editing by Mary Milliken, Alistair Bell, Rod Nickel, Don Durfee and Michael Perry)