Rocks and bottles flew through the air in Portland, Oregon, Saturday afternoon as a self-described libertarian group clashed with antifa counter-protesters. 

Police in heavy riot gear declared Patriot Prayer's rally in downtown Portland a civil disturbance and ordered everyone to leave, The Oregonian reported, after demonstrators were seen hurling projectiles into the crowds.

"There will be a significant law enforcement presence in the area of the demonstration due to past threats and acts of violence," Portland police wrote in a statement earlier Saturday afternoon. "Persons attending any of the events should not bring any weapons or items that can be used as weapons to any of the events."

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Groups on opposites sides of a downtown street began hurling objects at each other.

One side was chanting “USA!” "USA!" while the others chanted "fascists retreat," CNN reported.

Portland police posted photos online of the weapons and objects seized from the crowds, many of which included the Confederate battle flag. 

One reporter for The Oregonian, Eder Campuzano, tweeted that he was hit in the head with an object and posted a photo of his head bleeding.

Campuzano said he was treated by medics and that he was okay.

The event, which had a permit from the city, was organized by far-right Senate candidate Joey Gibson, who leads Patriot Prayer.

In a “Hate Watch” report issued before the rally, the Southern Poverty Law Center (SPLC) — watchdog organization that monitors hate groups —  warned “threats of violence” were looming over the upcoming rally. The SPLC suggested the Portland rally could be “another Charlottesville," referring to a Virginia clash last year between "alt-right" white nationalists and counter-protesters that left one counter-protester dead.