Los Angeles, California - A US senator from California was forcibly removed after interrupting a news conference being held by the US homeland security chief on Thursday.

"I'm Senator Alex Padilla. I have questions for the secretary," he said as two men pushed and shoved him from the room where Kristi Noem was speaking about controversial immigration arrests that have rocked America's second-biggest city.

Footage of the incident showed security agents forcing the senator to the floor and handcuffing him.

Padilla, one of two Democratic senators representing California in the upper chamber of Congress, can be heard trying to ask Noem about the targeting of immigrants.

Donald Trump White House says Trump won't allow "mob rule" as California leaders push back

Response to the incident was rapid.

California Governor Gavin Newsom said Padilla "is one of the most decent people I know."

"This is outrageous, dictatorial, and shameful. Trump and his shock troops are out of control. This must end now," he wrote on social media.

Los Angeles Mayor Karen Bass called the episode "absolutely abhorrent and outrageous."

"He is a sitting United States Senator. This administration's violent attacks on our city must end."

Noem's press conference came after almost a week of protests in Los Angeles sparked by an immigration crackdown ordered by President Donald Trump.

The mostly peaceful protests have been marred by eye-catching violence, including the torching of cars and rocks thrown at police officers.

The White House responded with overwhelming force, sending 4,700 troops to the city, despite objections from local officials and the police, who said they had the manpower and ability to handle the demonstrations.