Protests have broken out across the US after a public observer was fatally shot at an ICE raid in Minneapolis, Minnesota.

It's the latest flashpoint in US President Donald Trump's widespread crackdown on immigration, which last year saw thousands of military troops patrolling city streets.

Here's what to know.

What happened in Minneapolis?

An immigration agent shot and killed a 37-year-old woman in her car during a raid in the south of Minneapolis, Minnesota, on Wednesday, local time.

Renee Nicole Good had been at the scene as a legal observer — a volunteer who monitors government officers at protests and operations, documenting interactions and deterring misconduct.

US President Donald Trump claimed the agent fired in self-defence, accusing Ms Good of being a "professional agitator".

"The woman driving was very disorderly, obstructing and resisting, who then violently, wilfully and viciously ran over an ICE officer," he wrote on social media.

But witness statements and footage of the incident, verified by the ABC, raise doubts about that account.

Videos taken from different vantage points show an officer approaching a maroon Honda SUV stopped in the middle of the road, demanding the driver open the door and grabbing at the handle.

The Honda Pilot begins to pull forward as its wheels turn to the right in an apparent effort to head up the street and away from the scene.

An officer standing in front of the vehicle pulls his weapon and immediately fires at least two shots into the SUV at close range.

Minneapolis Mayor Jacob Frey slammed the president's description of the incident, calling it a "garbage narrative".

"Having seen the video myself, I want to tell everybody directly — that is bullshit," he said at a press conference.

Minnesota Governor Tim Walz said the Trump administration's narrative of the event was "propaganda".

The shooting quickly drew crowds of angry protesters and by evening, hundreds had gathered for a vigil to mourn Ms Good's death and urge public resistance of immigration enforcers.

A woman holds a protest sign at the vigil for Renee Nicole Good. (Reuters: Tim Evans)

What is ICE?

ICE, which stands for Immigration and Customs Enforcement, is a law enforcement agency under the Department of Homeland Security.

It's responsible for enforcing the US's immigration laws and is tasked with arresting people it believes are in the country illegally.