Fort Bragg, North Carolina - President Donald Trump on Tuesday claimed Los Angeles was being invaded by a "foreign enemy" and vowed to "liberate" the city after days of protests sparked by aggressive immigration raids.

In a hardline speech at one of the country's biggest army bases, Trump described protesters as "animals" and got troops to boo the names of California Governor Gavin Newsom and ex-president Joe Biden.

Trump has deployed thousands of troops, including 700 active duty US Marines, to Los Angeles, despite California authorities saying the move is unnecessary and will inflame the situation.

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Newsom has called Trump's actions "dictatorial."

"This anarchy will not stand. We will not allow federal agents to be attacked, and we will not allow an American city to be invaded and conquered by a foreign enemy," Trump told troops at Fort Bragg in North Carolina.

Trump described the protesters as "animals" who "proudly carry the flags of other countries."

"What you're witnessing in California is a full-blown assault on peace, on public order and national sovereignty, carried out by rioters bearing foreign flags with the aim of continuing a foreign invasion of our country," the US president said.

Trump linked the protesters to what he called "uncontrolled migration" and said that Europe – which his administration has repeatedly berated on the subject – must act too.

"As the entire world can now see, uncontrolled migration leads to chaos, dysfunction, and disorder," Trump said.

"And you know what? They have it in Europe, too. It's happening in many of the countries of Europe. They better do something before it's too late."