A U.S. federal agent shot a motorist in Chicago on Saturday as a judge blocked President Donald Trump's bid to deploy troops to Portland, with tensions spiking in both Democratic cities where the U.S. leader says a security emergency requires military intervention.

They are the latest flashpoints in the Trump administration's aggressive mass deportation campaign, which has seen heavily militarized raids and protests in places like Los Angeles and Washington.

Trump has repeatedly called Portland "war-ravaged" and riddled with violent crime, but in Saturday's court order, U.S. District Judge Karin Immergut wrote that "the President's determination was simply untethered to the facts."

"Defendants presented evidence of sporadic violence against federal officers and property damage to a federal building," Immergut wrote, but they failed to demonstrate "that those episodes of violence were part of an organized attempt to overthrow the government as a whole."

Protests in Portland did not pose a "danger of rebellion," and "regular law enforcement forces" could handle such incidents, Immergut added.

Oregon Senator Ron Wyden applauded the order, saying the "victory supports what Oregonians already know: we don't need or want Donald Trump to provoke violence by deploying federal troops in our state."

The incident came as Illinois Governor JB Pritzker said Washington had ordered him to deploy his state's National Guard troops, or federal authorities would do so over his objections.

"The Trump administration's Department of War gave me an ultimatum: call up your troops, or we will. It is absolutely outrageous and un-American to demand a Governor send military troops within our own borders and against our will," Pritzker said on X.

The U.S. Department of Homeland Security (DHS) said the shooting in Chicago took place Saturday morning after agents were "boxed in by 10 cars."

"Agents were unable to move their vehicles and exited the car. One of the drivers who rammed the law enforcement vehicle was armed with a semi-automatic weapon," DHS assistant secretary Tricia McLaughlin said in a statement.

"Law enforcement was forced to deploy their weapons and fire defensive shots at an armed U.S. citizen," she added.

AFP could not independently verify the DHS version of events.

The agency said the motorist "drove herself to the hospital to get care for wounds."

McLaughlin also accused Chicago police of "leaving the shooting scene," with officers refusing "to assist us in securing the area."

Chicago police told local broadcaster Fox 32 that officers responded to the scene but the department "is not involved in the incident or its investigation. Federal authorities are investigating this shooting."