"Nazis go home," they yell in videos of the incident on Sunday.
Other anti-fascists - or Antifa - set ablaze a blue, black and white version of the US flag that signifies support for the police in a gesture against police brutality.
Columns of police in riot gear, supported by officers from the Department of Homeland Security, stand between the alt-right rally-goers and the Antifa counter-protesters, and although there are only minor skirmishes between them, clashes between the police and Antifa result in the arrest of at least 14 people.
Sunday was just the latest occasion on which Antifa activists and alt-rightists have converged on cities across the US with the intention of fighting.
For Antifa, direct confrontation is a key strategy intended to shut down far-right demonstrations and block platforms for hate speech.
Over the past few months, the alt-right - a loosely knit coalition that includes white supremacists and neo-Nazis - has also focused on building a larger street presence to confront their opponents.
Although they have many disagreements with US President Donald Trump, they have generally supported his far-right policies.
Since Trump's inauguration on January 20, the alt-right has sought to build broader alliances with neo-Nazi groups and more mainstream Trump supporters in order to fight Antifa, say analysts and activists.
Patriot Prayer, a far-right Christian group headed by alt-right activist Joey Gibson, was behind the Portland rally. While Gibson says the protests he holds in Portland are for the promotion of free speech, white supremacists - such as Portland stabbing suspect Jeremy Christian - have attended the events.
Christian is accused of killing Ricky Best, 53, and Taliesin Namkai-Meche, 23, on a light rail train when they intervened to stop his harassment of a pair of teenage girls, one of whom was wearing a hijab.
A third man who intervened, 21-year-old Micah Fletcher, was severely injured.
READ MORE: Alt-right rally draws protests in Portland, Oregon
The fatal attack came just a week after Sean Christopher Urbanski, a 22-year-old studying at the University of Maryland, allegedly killed Richard Collins III, a 23-year-old African American student at a nearby university.
The assailant was a member of a Facebook group titled the "Alt-Reich", a play on words on the German Third Reich and the alt-right. Police are investigating the incident as a hate crime.
'There will be blood'
Speaking to Al Jazeera by telephone, Gibson denied any links to Christian and insisted that his group evicted the alleged killer from a recent protest. Christian was recently filmed making Nazi salutes and calling for the death of Jews, Muslims and "fake Christians" at one of Gibson's events before eventually being ejected.
"This is about promoting freedom and promoting spirituality," Gibson argued. "Conservatives and libertarians have to get off Facebook and get onto the streets because we've let the left have them for too long."
"Antifa has had no impact on me and my free speech, but they've had more of an impact on others' free speech because they try to make threats," he said.
Gibson decried local authorities for supposedly caving into left-wing pressure, citing the Portland municipality's decision to cancel the city's annual Rose Festival parade in April after anti-fascists promised to confront far-right participants there.
"Antifa is all talk," Gibson added. "To be honest, some of the people in that group are really good, passionate people, but the rest of them are just kids who cover their faces up and run around burning stuff down."
Anti-fascists argue that the guarantee of free speech is intended to protect against government censorship, not to provide platforms on which to espouse far-right views. With new Antifa groups popping up nationwide, they insist they are prepared for more confrontations.
One Portland-based anti-fascist activist, who spoke to Al Jazeera on the condition of anonymity for fear of legal repercussions and having his identity exposed by alt-rightists, said local Antifa groups are committed to shutting down far-right protests in the city.
"We've given them the opportunity to disappear without direct confrontation, and we've allowed them to walk through the streets," he told Al Jazeera by telephone.
"They've gotten cocky and need to be brought down a level, and sometimes that means in the most literal sense.
"In my opinion, I do think there will be blood in Portland - on whose side, I can't say. But someone's going to bleed," he concluded.
A local Republican Party official has advocated using citizen militias to protect Republicans. Multnomah County Republican Party chair James Buchal recently told The Guardian that the party should deploy the Oath Keepers and Three Percenters, gun-toting far-right groups, as security for their events.
'Increased street fighting presence'
While many far-right and neo-Nazi groups have been active for decades, the alt-right was propelled to the spotlight for its vocal support of Trump during his electoral campaign.
Although it had mostly been confined to chat rooms and social media outlets until recently, the movement views showing up for street fights as critical to its success, said Matthew Lyons, author of Ctrl Alt Delete, a collection of essays examining the movement.
"It makes sense that [building a street presence] is something that they've been focusing energy on in the recent time, partly in response to the upsurge of anti-fascist activism and the general upsurge of physical confrontations," he told Al Jazeera by telephone.
On April 15, hundreds of Antifa activists and Trump supporters brawled in Berkeley, California, using homemade shields, sticks, batons, pepper-spray and other makeshift weapons.
Although deeply divided by ideological differences, mainstream Trump supporters, nationalists, the alt-right and other white supremacists banded together to fight Antifa.
During the street fighting, Nathan Damigo, a former Marine and leader of the white supremacist group Identity Evropa, was filmed sucker punching 20-year-old Antifa activist Louise Rosealma, also known as Emily Rose Marshall.
The effort to engage in more street confrontations is also partly motivated by a general disillusionment with Trump; many alt-rightists resent the president's reneging on electoral promises like halting US military intervention in other countries, said Lyons.
Alt-rightists have been trying to "build alliances in several directions," Lyons explained. While reaching out to more hardline neo-Nazi groups, the movement has also rallied against Antifa alongside self-described "patriot groups" such as the Oath Keepers.
"That is very important because I think Berkeley was the first example that I was aware of with patriot groups and alt-right groups being involved in the same demonstration in an organised way."
Both sides have also made expansive use of doxing, the tactic of publishing private or identifying information about opponents on the internet.
Far-right users of 4chan, an image board website where members post anonymously, have also started maintaining an online database to identify Antifa activists.
After the video of Damigo punching Rosealma went viral on social media outlets, alt-rightists dug through her personal history and shared her private information across the internet.
Upon discovering that Rosealma had previously been a sex worker, they published her pornographic videos on websites and posted links to them on her grandmother's Facebook page, according to local media reports.
'Anxious to defeat them'
On Saturday, a local branch of the Proud Boys - a far-right nationalist group headed by Vice cofounder and Rebel Media host Gavin McInnes - held a rally for free speech in Boulder, Colorado. They were greeted by hundreds of counter-protesters, including the Rocky Mountain Antifa. Local media reported several arrests.
Next weekend, anti-Muslim protesters will hold the National March Against Sharia, with events scheduled in more than 23 cities nationwide.
Hosted by ACT for America, one of the largest anti-Muslim groups in the US, the march will be the target of Antifa actions in many cities and towns, activists say.
With events like these growing in intensity and frequency, Antifa groups argue that direct confrontation is often necessary to prevent racist groups from being given a platform to espouse their views.
Near Houston, Texas, the Houston Socialist Movement plans to disrupt a National March Against Sharia protest in nearby La Porte.
David Michael Smith, an organiser with the Houston Socialist Movement, said his organisation has faced off with neo-Nazis and other far-right groups on a regular basis since the months leading up to the presidential elections in November.
"Our goal is to outnumber and out-shout them and drive them off the streets," he said.
"We are anxious to politically defeat them," he explained. "We don't believe there should be platforms for fascists because history teaches us we can't allow that."
Hoku Jeffrey, a national organiser with By Any Means Necessary (BAMN), a left-wing civil rights group, maintains that militant anti-fascism is necessary to prevent the growth of alt-right groups and others like them.
BAMN has participated in the recent mass protests in Berkeley, California, among them the demonstration that resulted in the cancellation of a speech by far-right provocateur Milo Yiannopoulos in February when Antifa hurled objects at the building and set fires outside.
"This not a question of abstract free speech; it is a question of the right of immigrants, Muslims, other oppressed minorities, and women to live and live safely, together with countless others who vehemently oppose these violent racist attacks," he told Al Jazeera by email.
Jeffrey argues that Trump supporters and the alt-right are acting "out of a desperate sense of embattlement" and that resistance to the Trump administration's policies will continue to grow.
"More people, especially growing numbers of immigrants and young people, are taking direct action to obstruct Trump's policies and confront his most dangerous racist and neo-fascist supporters."
Author: Patrick Strickland