The National Guard will be deployed to Portland, Oregon, for the next two months, following an order by US President Donald Trump.

At least 200 National Guard members will be deployed to the city to "protect federal property" where protests are "occurring or likely to occur", according to a memo sent by US Defence Secretary Pete Hegseth on Sunday.

Trump on Saturday said he had authorised the use of "full force" if needed to suppress protests targeting immigration detention centres.

Oregon has responded by suing the Trump administration, arguing that the deployment of the National Guard to Portland is "unlawful".

The lawsuit, filed on Sunday by Oregon Attorney General Dan Rayfield, called the move "provocative and arbitrary", and said it "threatens to undermine public safety by inciting a public outcry".

The deployment marks a further expansion of troop deployments in US cities, amid a wider crackdown by the Trump administration on illegal immigration.

Trump claimed it would help protect "any of our ICE Facilities under siege from attack by Antifa, and other domestic terrorists", characterising the city as "War ravaged" in a Truth Social post.

Democratic lawmakers in Oregon have pushed back, rejecting Trump's assertion that Portland needed federal intervention.

"There is no national security threat in Portland. Our communities are safe and calm," said Oregon Governor Tina Kotek on Saturday.

The Immigration and Customs Enforcement (ICE) facility in Portland has been targeted by protesters since early June, sometimes leading to violent clashes.

As of 8 September, the US Attorney's Office had brought federal charges against 26 people for crimes including arson, assaulting a police officer and resisting arrest.

The DHS said on Friday that demonstrators had "repeatedly attacked and laid siege to an ICE processing centre" in Portland.

The department stated that several individuals had been arrested and charged with federal offences in a post on social media.

"Rose City Antifa, a recently designated domestic terrorist organisation, illegally doxed ICE officers," it wrote.

"They published their home address online and on public flyers. Individuals associated with Antifa also sent death threats to DHS personnel."

Rose City Antifa has said it was not responsible for the flyers.

Earlier this week, Trump signed an order formally designating Antifa as a domestic terrorist organisation.

Antifa, short for "anti-fascist", is a loosely organised movement of primarily far-left activists.

Legal experts have pointed out that there is no legal mechanism in the US that would formally establish any group as a domestic terror organisation. Such efforts, they said, could face constitutional challenges under the First Amendment, which protects free speech and assembly.

Democratic lawmakers have criticised both the president's rhetoric and the reported actions of ICE agents in the state.

Oregon Senator Ron Wyden said on Friday that there were "credible" reports that federal agents "may be replaying the 2020 playbook" - a reference to federal forces being deployed in response to protests over the murder of George Floyd, a black man who died in police custody.

"I urge Oregonians not to fall into Trump's attempt to incite violence," Wyden said.

Local lawmakers have also accused ICE of going after people who are not an actual danger to society.

"ICE has said they're targeting people for arrest and detainment who have committed crimes. That's what they told us. But that's not what we are seeing," said Democratic house representative Suzanne Bonamici.

Lawmakers cited recent incidents, including the detention of a father outside his child's preschool and a wildland firefighter who was arrested while battling fires in the Olympic National Forest.

They also pointed to a statistic published by the Cato Institute, a US think tank based in Washington DC, which reported that 65% of people detained by ICE had no criminal convictions.

Despite the backlash from Democrats, the move has drawn support from some Republican officials.

US Labour Secretary Lori Chavez-DeRemer said she had seen how "lawlessness" had turned Portland into a "crime-ridden warzone".

Chavez-DeRemer, who previously served as a Republican house representative for Oregon, thanked Trump "for taking action to keep our ICE facilities protected and Make America Great Again".

Earlier this year, Trump deployed the National Guard to Los Angeles and Washington DC. Federal agents are expected to arrive in Memphis in Tennessee next week.

In Los Angeles, the president ordered 2,000 federal personnel to deal with unrest over raids on undocumented migrants. Clashes erupted over several days, and tear gas was used to disperse protesting crowds.

A federal judge in California ruled earlier this month that the National Guard deployment in Los Angeles was illegal, and that it violated the Posse Comitatus Act, which limits the power of the federal government to use military force for domestic matters.

It is unclear whether the president has legal ground to deploy federal forces to Oregon.(BBC)