US deploys Marines to Los Angeles as police break up fourth day of protests

The US military will temporarily deploy about 700 Marines to Los Angeles until more National Guard troops can arrive on the fourth day of street protests over US President Trump's immigration policies.

This follows tensions after the US President activated the National Guard on Saturday following street protests that erupted in response to immigration raids in Southern California. It is the biggest flashpoint yet in the Trump administration's efforts to deport migrants living in the country illegally.

Late on Monday police began to disperse hundreds of demonstrators who gathered outside a federal detention center in downtown Los Angeles where immigrants have been held.

National Guard forces had formed a human barricade to keep people out of the building, following troops of Los Angeles police starting to push people from the scene and firing "less lethal" munitions such as gas canisters.

California sued the Trump administration to block deployment of the National Guard and the Marines on Monday, arguing that it violates federal law and state sovereignty.

US Marines have been deployed domestically for major disasters such as Hurricane Katrina and the September 11, 2001, attacks, but it is extremely rare for US military troops to be used for domestic policing.

For now, the Trump administration was not invoking the Insurrection Act, which would allow troops to directly participate in civilian law enforcement, according to a US official speaking on condition of anonymity.

The Pentagon confirmed on Monday that a contingent of 2,000 National Guard troops would be doubled to 4,000. President Trump also added that he felt he had no choice but to increase the level of force to prevent violence from spiraling out of control.

He also supported a suggestion by his US law enforcement officer Tom Homan that California Governor Gavin Newsom should be arrested over possible obstruction of his administration's immigration enforcement measures. 

Democrats said President Trump's decision to deploy military force to handle the protests amounts to an abuse of presidential power, and California's lawsuit claimed it was illegal.

Protests also sprang up in at least nine other US cities on Monday, including New York, Philadelphia and San Francisco, according to local US news outlets.

The Trump administration has argued that Democratic President Joe Biden's administration allowed far too many immigrants to enter the country and that Democratic-run cities such as Los Angeles are improperly interfering with efforts to deport them. The US President has pledged to deport record numbers of people who are in the country illegally and to lock down the US-Mexico border, setting a goal of at least 3,000 daily arrests.

The last time the military was used for direct police action under the Insurrection Act was in 1992, when the California governor at the time asked President George H.W. Bush to help respond to Los Angeles riots over the acquittal of police officers who beat Black motorist Rodney King.

More than 50 people were killed in the 1992 riots, which also caused some $1 billion in damage over six days.

Federal allows the president to deploy the National Guard if the nation is invaded, if there is "rebellion or danger of rebellion," or the president is "unable with the regular forces to execute the laws of the United States."