US President Donald Trump on Monday accused protesters of insurrection as police patrolled central Los Angeles after a weekend of clashes triggered by immigration raids.

Residents were ordered not to gather in the city's downtown where demonstrators had torched cars and security forces fired tear gas in violence that local officials stressed remained localized.

Trump posted that he had deployed National Guard troops "to deal with the violent, instigated riots" and "if we had not done so, Los Angeles would have been completely obliterated."

"The people are causing the problems are professional agitators and insurrectionists," he told reporters in Washington.

California's governor Gavin Newsom accused the president of deliberating stoking tensions by using the National Guard, a reserve military force usually controlled by state governors.

"This is exactly what Donald Trump wanted," Newsom said. "He flamed the fires."

The protests in Los Angeles, home to a large Latino population, were triggered by raids and dozens of arrests of what authorities say are illegal migrants and gang members.

On Monday morning, a heavy police presence stood watch over mostly deserted streets. A few protesters had remained overnight, with some lobbing projectiles and fireworks.

"You have the National Guard with loaded magazines and large guns standing around trying to intimidate Americans," protester Thomas Henning told AFP at the scene of the standoff Sunday.

Trump's border Tom Homan denied the Immigration and Customs Enforcement (ICE) agency had conducted any raids, describing them as arrests linked to cartels in Mexico and Colombia.

"It wasn't an immigration raid," he told MSNBC, saying it was an investigation into money laundering, tax evasion and customs fraud. (AFP)