Roughly 500 US Marines based out of the Marine Corps Air Ground Combat Centre in California have been mobilised to respond to the protests in Los Angeles, according to three people familiar with the matter.

They will join the thousands of National Guard troops that were activated by President Donald Trump over the weekend without the consent of California’s governor or LA’s mayor.

The deployment of the full Marine battalion marks a significant escalation in Trump’s use of the military as a show of force against protesters, but it is still unclear what their task will be once in LA, the sources said.

Like the National Guard troops, they are prohibited from conducting law enforcement activity like making arrests unless Trump invokes the Insurrection Act.

One of the people familiar with the Marine mobilisation said they will be augmenting the Guard presence on the ground in LA.

Over 2000 members of the California National Guard have been activated by the president, but only about 300 have been deployed to the streets of LA so far.

Those initial 300 people were on a routine National Guard drill weekend when they were mobilised, which is why they were able to arrive so quickly, the person familiar said; it can take up to 72 hours for other Guardsmen to be mobilised.

The Marines are expected to bolster some of the Guard members who have been deployed to LA in the last two days, this person said.

While their tasks have not been specified publicly, they could include assignments like crowd control or establishing perimeter security.

Lawyers within the Defence Department are also still finalising language around the use of force guidelines for the troops being mobilised, but the person familiar said it will likely mirror the military’s standing rules of the use of force.