US Homeland Security Secretary Kristi Noem says hundreds more federal agents are heading to Minneapolis, brushing aside demands by the city's Democratic leaders to leave after an immigration officer fatally shot a female protester.

In multiple television interviews, Ms Noem defended the actions of the officer who shot and killed 37-year-old Renee Nicole Good, whose death has sparked renewed protests nationwide against US President Donald Trump's aggressive immigration crackdown.

Ms Noem reiterated her claim that Ms Good's actions in the Midwestern city on Wednesday amounted to "domestic terrorism," and that the agent acted in self-defence when he fatally shot Ms Good in her car.

Prominent Democratic officials, including Minnesota Governor Tim Walz and Minneapolis Mayor Jacob Frey, have strongly disputed this narrative, saying viral footage from the scene shows Ms Good's vehicle turning away from the agent and posing no threat to his life.

Renee Nicole Good was shot and killed by an ICE officer in Minneapolis last week. (AP: Mike Householder)

Ms Noem, when pressed repeatedly by CNN about how she could make such definitive statements while an investigation into the incident had just begun, insisted she and the administration were in the right.

"Why are we arguing with a president who's working to keep people safe?" she said.

Speaking separately to the conservative Fox News network, Ms Noem said hundreds more officers would arrive Sunday and Monday, local time, to allow immigration agents "that are working in Minneapolis to do so safely".

If protesters "conduct violent activities against law enforcement, if they impede our operations, that's a crime, and we will hold them accountable to those consequences," Ms Noem told Sunday Morning Futures on Fox News.

'Extremely politicised'

Meanwhile, confrontations between federal agents and protesters continued on Sunday in Minneapolis, with officers seen using pepper spray against people holding signs outside an Immigration and Customs Enforcement (ICE) facility in the city.

Ms Noem accused Democrats of encouraging violence against immigration officers.

Thousands of people across multiple US cities have demonstrated since Wednesday's shooting. (AFP: Timothy Clary)

"These locals, if you look at what Governor Walz has said, if you look at what Mayor Frey has said, they've extremely politicised and inappropriately talked about the situation on the ground in their city," she told CNN's State of the Union.