Members of California's National Guard were seen on Sunday staging at the federal complex in downtown Los Angeles that includes the Metropolitan Detention Center, one of several sites of confrontations involving hundreds of people in the last two days.
Trump has said he is deploying 2000 California National Guard troops to Los Angeles to quell the protests, which he called "a form of rebellion".
The move came over the objections of Governor Gavin Newsome, marking the first time in decades that a state;s national guard was activated without a request from its governor, according to the Brennan Center for Justice.
Early on Sunday, the deployment was limited to a small area in downtown Los Angeles, with the rest of the city of four million people largely unaffected.
Their arrival follows two days of relatively small protests that began on Friday in downtown Los Angeles before spreading on Saturday to Paramount, a heavily Latino city south of the city, and neighbouring Compton.
As federal agents staged near a Home Depot in Paramount, demonstrators sought to block Border Patrol vehicles, with some hurling rocks and chunks of cement.
In response, federal agents in riot gear unleashed tear gas, flash-bang explosives and pepper balls.
Tensions were high after a series of sweeps by immigration authorities the previous day, as the week-long tally of immigrant arrests in the city climbed past 100.
A prominent union leader was arrested while protesting and accused of impeding law enforcement.
On Sunday morning, Homeland Security Secretary Kristi Noem said the National Guard would "keep peace and allow people to be able to protest but also to keep law and order".
The troops included members of the 79th Infantry Brigade Combat Team, according to a social media post from the Department of Defense that showed dozens of National Guard members with long guns and an armoured vehicle.
In a signal of the administration's aggressive approach, Defense Secretary Pete Hegseth also threatened to deploy active-duty Marines "if violence continues" in the region.
Newsom, a Democrat, described Trump's decision to call in the National Guard as a "provocative show of force" that would only escalate tensions, adding that Hegseth's threat to deploy Marines on US soil was "deranged behaviour".
Vermont Senator Bernie Sanders said the order by Trump reflected "a president moving this country rapidly into authoritarianism" and "usurping the powers of the United States Congress".
Several Republicans, meanwhile, have voiced support for the involvement of the National Guard.
Among them was Wisconsin Republican Senator Ron Johnson, who stopped short of backing Hegseth's threat to send in active-duty military personnel.
"My guess is the National Guard ought to take care of the situation," Johnson said.
