Marines were seen standing guard outside a federal building in Los Angeles on Friday as they started to take over some posts from National Guard members after protests erupted last week over immigration raids and President Donald Trump deployed the troops to the city.

Trump's decision to send troops to Los Angeles, despite California Governor Gavin Newsom's objections, has ignited a national debate on military involvement in law enforcement on US soil.

The number of National Guard troops is expected to rise to 2,000 by Wednesday and until then, the Marines are expected to provide support.