Protests live updates: Marines make 1st temporary detention in LA

Protests on Monday saw police slowly, methodically build up a massive presence outside of Los Angeles' federal buildings.

On the bullhorn, an officer was heard warning protesters -- who appeared to be angling to get back to the 101 Freeway and who had commandeered Los Angeles Street -- that they'd have five minutes to disperse the unlawful assembly.

An hour later, they still hadn't moved on the protesters who were jeering and taunting them, but behind them, Los Angeles Sheriff's SWAT teams had moved into the scene in armored cars with sound cannons and portable barriers. LAPD Cruisers and Suburbans closed ranks behind them, effectively sealing the street.

They moved as if in a brigade-sized military exercise, taking the high ground of the garage -- flooding the lower floors with officers then and pouring in from alleys and side streets. It was a pincer movement that sent some of the protesters scattering. They fired lots of less lethal rounds and flash bangs thundered. Everyone moved back.

Los Angeles' Temple Street had dozens of cruisers and hundreds of officers. Dozens of additional cruisers were also seen on Alameda Street with hundreds of officers.

-ABC News' Matt Gutman and Timmy Truong

As protests in Los Angeles enter their fourth night, photos from the scene show tense moments as protesters confronted authorities.

At one point, police said protesters near Temple Street and Los Angeles Street in downtown LA began throwing objects at police and police authorized the use of "less lethal munitions" in response.

Other photos show members of the California National Guard standing guard in front of the Edward R. Roybal Federal Building in downtown LA -- the site of protests over the weekend.

Los Angeles Mayor Karen Bass called on the Trump administration to stop immigration raids in the city, saying the fear and uncertainty they have created have led to the unrest.

“I am hopeful that the federal government will hear our plea: Stop the raids," Bass said. "This is creating fear and chaos in our city, and it is unnecessary. And I hope that we will be heard because our city is trying to move forward and I believe that the federal government should be supportive of us moving forward."

Bass said she spoke to members of the Trump administration over the weekend, urging the federal government not to deploy the National Guard. Bass said she has not spoken directly to President Donald Trump.

"It makes me feel like our city is actually a test case, a test case for what happens when the federal government moves in and takes the authority away from the state or away from local government," she told reporters during a news conference Monday. "I don't think that our city should be used for an experiment."

Los Angeles Police Department Chief Jim McDonnell acknowledged the deployment of 700 Marines to the city and said that it presents a "logistical challenge" and "risks confusion."

McDonnell and Los Angeles Mayor Karen Bass spoke at a press conference Monday while hundreds of protesters remain in downtown L.A.

"We're also aware of reports that the President intends or has deployed US Marines to Los Angeles. The introduction of federal military personnel without direct coordination creates logistical challenges and risks confusion during a critical incident," McDonnell said of the Trump administration's decision.

McDonnell also said the LAPD has mobilized officers, allowing them to deploy an additional 400 officers to the scene.

-ABC News' Matt Claiborne