Thousands of demonstrators have marched past Trump Tower as the sun set in downtown Chicago, protesting US President Donald Trump's threats to flood the city with immigration agents.

The protest came after fears of increasing deportations chilled a normally raucous Mexican Independence Day celebration, as Trump signalled his intention to ramp up immigration enforcement on social media.

In a social media post depicting himself as a US military officer from the movie Apocalypse Now, Trump wrote "I love the smell of deportations in the morning" above an image of himself in uniform juxtaposed against flames and Chicago's skyline.

For many protesters, the threats felt personal.

Tracy Quinonez, 50, said her father, who recently died, came to the US from Guatemala as a refugee.

"I'm here for

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