US President Donald Trump says "domestic terrorists" and "anarchists" have taken over Seattle, warning the state's governor that if he doesn't take back control, "I will".
Protesters declared a police-free "autonomous zone" in the city earlier this week, before storming Town Hall to demand the mayor's resignation.
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Signs reading "You are now leaving the USA" and "This space is now the property of the Seattle people" have been plastered around the so-called Capitol Hill Autonomous Zone, which spans six blocks around the abandoned Seattle Police Department's East Precinct building.
The defaced sign of the police building now reads "Seattle people department".
The move follows weeks of violent clashes between Black Lives Matter protesters and police in Seattle and sparked a furious response from Trump.
"Domestic Terrorists have taken over Seattle, run by Radical Left Democrats, of course. LAW & ORDER!" he tweeted.
In another tweet, the President demanded Washington Governor Jay Inslee and Seattle Mayor Jenny Durkan "take back" the city.
"Radical Left Governor (Jay Inslee) and the Mayor of Seattle are being taunted and played at a level that our great Country has never seen before.
"Take back your city NOW. If you don't do it, I will. This is not a game. These ugly Anarchists must be stooped IMMEDIATELY. MOVE FAST!"
Asked at a media conference about the zone, Inslee said he knew "nothing about that", leaving many incredulous.
But local media reports an autonomous zone appears to be a peaceful, camp-out sanctuary for protesters, who have been sharing snacks, handing out free face masks, and holding after-dark film screenings.
It's also a place where they have planned next steps as they demand police reforms in the wake of the death of unarmed black man George Floyd, which sparked the protests.
The Seattle Times reported one of the protesters, Sarah Tornai, said the autonomous zone meant people wanted to be "autonomous from the way the Seattle Police Department has been policing them".
She said there were plans for the East Precinct building to become a community centre for education and local community programmes.
There have been violent clashes between protesters and police in Seattle during weeks of protests sparked by Floyd's death.
Police have used tear gas, pepper spray and other less-lethal weapons against crowds, while on the weekend, authorities said rocks, bottles and explosives were thrown at officers.
Police rolled back from the area this week in an effort to de-escalate tensions, saying they would only now attend the area to respond to 911 emergency calls.
A Black Lives Matter group has sued the Seattle Police Department over its use of tear gas, pepper spray and other weapons on crowds of protesters.
Durkan and Police Chief Carmen Best have apologised to demonstrators for the heavy-handed response of police and set a 30-day ban on the use of tear gas.
Protesters stormed the city's town hall on Tuesday night, supported by a local councillor, to demand the resignation of Durkan over her handling of civil unrest in the city.
In a statement, the office for the mayor said she remained committed to "actual steps on policing".
"As the person who originally investigated the Seattle Police Department [SPD] for the unconstitutional use of force, Mayor Durkan believes that SPD can lead the nation on continued reforms and accountability, but knows this week has eroded trust at a time when trust is most crucial," the statement said, according to Fox News.