US President Donald Trump on Saturday said he was directing the military to deploy to Portland, Oregon and to protect federal immigration facilities against "domestic terrorists", saying he was authorising them to use "full force, if necessary."

Ordering the latest crackdown on a Democrat-led city, Trump said in a social media post that he was directing Defence Secretary Pete Hegseth "to provide all necessary Troops to protect War ravaged Portland, and any of our ICE Facilities under siege from attack by Antifa, and other domestic terrorists."

Portland Mayor Keith Wilson, responding to Trump's order, said: "The number of necessary troops is zero, in Portland and any other American city. The president will not find lawlessness or violence here unless he plans to perpetrate it."

In a press conference on Friday, Wilson and other local leaders urged calm in the face of an apparent influx of federal officers that the mayor said did not come at the request of the city.

"This may be a show of force, but that's all it is. It's just a big show," he said.

US Senator Ron Wyden, a Democrat from Oregon, wrote on X that Trump "may be replaying the 2020 playbook and surging into Portland with the goal of provoking conflict and violence."

In 2020, protests erupted in downtown Portland, the Pacific Northwest enclave with a reputation as a liberal city, following the killing in Minneapolis of George Floyd.

The protests dragged on for months and some civic leaders at the time said they were spurred rather than quelled by Trump’s deployment of federal troops.

Oregon Governor Tina Kotek, a Democrat, said her office was asking the White House for more information.

"There is no national security threat in Portland. Our communities are safe and calm," Kotek said on X. (Reuters)