Small scuffles broke out on Saturday as police in Portland, Oregon, deployed “flash bang” devices and other means to disperse hundreds of right-wing and self-described anti-fascist protesters.

There were four arrests and officers seized “multiple weapons throughout the day”, the Portland Police Bureau said.

Demonstrators aligned with Patriot Prayer and an affiliated group, the Proud Boys, had gathered at about noon in a riverfront park.

Hundreds of demonstrators faced them from across the street, holding banners and signs with opposition messages such as: “Alt right scum not welcome in Portland”.

Police push protesters back with tear gas and flash-bang grenades
Police push protesters back with tear gas and flash-bang grenades (AP Photo/John Rudoff)

Some chanted “Nazis go home” as officers stood in the middle of the four-lane boulevard, essentially forming a wall to keep the two sides separated.

The counter-protesters were made up of a coalition of labour unions, immigrant rights advocates, democratic socialists and other groups. They included people dressed as clowns and a brass band blaring music.

The rally organised by Patriot Prayer leader Joey Gibson was the third to roil Portland this summer. Two previous events ended in bloody fistfights and riots, and one counter-protester was sent to hospital with a skull fracture.

This time, Mr Gibson changed the venue from a federal plaza outside US District Court to a waterfront park so that some of his Oregon supporters could carry concealed weapons as they demonstrated.

Mr Gibson disputed the group’s classification by some as a hate group.

Portland police keep Patriot Prayer affiliates separate from antifa protesters
Portland police keep Patriot Prayer affiliates separate from antifa protesters (AP Photo/John Rudoff)

“We’re here to promote freedom and God. That’s it,” he told Portland TV station KGW while walking with demonstrators. “Our country is getting soft.”

Protesters saw a significant police presence that included bomb-sniffing dogs and weapons screening checkpoints.

In a statement, police said weapons would be seized if there was a violation of law and added that it was illegal in Portland to carry a loaded firearm in public unless a person had a valid Oregon concealed handgun licence.

Among the things police confiscated were long sticks and homemade shields.

Just before 2pm, police in riot gear ordered people to leave an area downtown, saying demonstrators had thrown rocks and bottles at officers.

Rally organiser Joey Gibson
Rally organiser Joey Gibson (Mark Graves /The Oregonian via AP)

“Get out of the street,” police announced via loudspeaker.

The Portland events have taken on out-sized significance after a Patriot Prayer sympathiser was charged with fatally stabbing two men who came to the defence of two young black women — one in a hijab — whom the attacker was accused of harassing on a light-rail train in May 2017.

A coalition of community organisations and a group representing more than 50 tribes warned of the potential for even greater violence than previous rallies if participants carried guns. It called on officials to denounce what it called “the racist and sexist violence of Patriot Prayer and Proud Boys” and protect the city.

Self-described anti-fascists — or “antifa” — have been organising anonymously online to confront Patriot Prayer and the Proud Boys in the streets.

Organisers say that while Patriot Prayer denies being a white supremacist group, it affiliates itself with known white supremacists, white nationalists and neo-Nazi gangs.