Los Angeles, Jun 7 (AP) Federal immigration authorities arrested 44 people on Friday across Los Angeles, prompting clashes outside at least one location as law enforcement threw flash bangs to try to disperse a crowd that had gathered to protest the detentions.

Immigration and Customs Enforcement officers and agents executed search warrants at three locations, said Yasmeen Pitts O'Keefe, a spokesperson for Homeland Security Investigations.

But immigration advocates said they were aware of arrests at seven locations, including two Home Depots, a warehouse in the fashion district and a doughnut shop, said Angelica Salas, executive director for the Coalition of Humane Immigrant Rights, or CHIRLA.

In the fashion district, agents served a search warrant at a business after they and a judge found there was probable cause the employer was using fictitious documents for some of its workers, US Attorney's Office spokesperson Ciaran McEvoy confirmed.

In Los Angeles, Mayor Karen Bass said the activity was meant to “sow terror”.

Federal immigration authorities have been ramping up arrests across the country to fulfill President Donald Trump's promise of mass deportations.

Todd Lyons, the head of US Immigration and Customs Enforcement, defended his tactics earlier this week against criticism that authorities are being too heavy-handed.

He has said ICE is averaging about 1,600 arrests per day and that the agency has arrested “dangerous criminals”.

Protests recently broke out after an immigration action at a restaurant in San Diego and in Minneapolis, when federal officials in tactical gear showed up in a Latino neighbourhood for an operation they said was about a criminal case, not immigration.

Dozens of protesters gathered Friday evening outside a federal detention centre in Los Angeles where they believed those arrested had been taken, chanting “set them free, let them stay!” Other protesters held signs that said “ICE out of LA!” while others led chants and shouted from megaphones. Some scrawled graffiti on the building facade.

Officers holding protective shields stood shoulder to shoulder to block an entrance.

Some tossed tear gas canisters to disperse the crowd. Officers wearing helmets and holding batons then forced the protesters away from the building by forming a line and walking slowly down the street.

“Our community is under attack and is being terrorised. These are workers, these are fathers, these are mothers, and this has to stop. Immigration enforcement that is terrorizing our families throughout this country and picking up our people that we love must stop now,” Salas, of CHIRLA, said at an earlier press conference while surrounded by a crowd holding signs protesting Immigration and Customs Enforcement.

Yliana Johansen-Mendez, chief programme officer for the Immigrant Defenders Law Center, said her organisation was aware of one man who was already deported back to Mexico after being picked up at a Home Depot on Friday morning.

The man's family contacted her organisation and one of their attorneys was waiting for hours to speak to him inside the detention centre, she said.

Authorities later said he had already been removed, and the man later contacted his family to say he was back in Mexico.

Videos from bystanders and television news crews captured people being walked across a Home Depot parking lot by federal agents as well as clashes that broke out at other detention sites.

KTLA showed aerial footage of agents outside a clothing warehouse store in the fashion district leading detainees out of a building and toward two large white vans waiting in a parking lot.

The hands of the detained individuals were tied behind their backs. The agents patted them down before loading them into the vans. The agents wore vests with the agency acronyms FBI, ICE and HSI. Armed agents used yellow police tape to keep crowds on the street and sidewalk away from the operations.

Officers throw smoke bombs to disperse crowd Aerial footage of the same location broadcast by KABC-TV showed officers throwing smoke bombs or flash bangs on the street to disperse the people so they could drive away in SUVs, vans and military-style vehicles.

The station showed one person running backward with their hands on the hood of a moving white SUV in an apparent attempt to block the vehicle.

The person fell backward, landing flat on the ground. The SUV backed up, drove around the individual and sped off as others on the street threw objects at it.

Immigrant-rights advocates used megaphones to speak to the workers, reminding them of their constitutional rights and instructing them not to sign anything or say anything to federal agents, the Los Angeles Times reported.

Katia Garcia, 18, left school when she learned her father, 37-year-old Marco Garcia, may have been targeted.

Katia Garcia, a US citizen, said her father is undocumented and has been in the US for 20 years. “We never thought this would happen to us,” she told the Los Angeles Times.

Pitts O'Keefe said in a statement that one additional person was arrested for obstruction. The California branch of the Service Employees International Union said its president was arrested while exercising his right to observe and document law enforcement activity. (AP) PY