A heavy police presence largely kept members of the Proud Boys and other far-right groups separated from far-left, anti-fascist activists at a downtown park Saturday, mostly avoiding violent clashes that have marred earlier confrontations.

At least 13 people were arrested, and four people have minor injuries, according to Portland Police. Although the day was largely peaceful, police said they seized weapons such as metal and wooden poles, bear spray and shields from demonstrators.

At one point, the far-right organizers asked for police to escort them from the area.

Joe Biggs, a former InfoWars staffer who organized the far-right rally along with the head of the alt-right Proud Boys, told KGW that his side made their point with a show of strength in Portland.

“We came in, we just did a march peacefully, we came in, planted our flag and came out, and they’re chasing us right now," he said. "We had a good time, said a prayer, said the national anthem and rolled out. That’s always been the plan."

Multnomah County Sheriff's Office Sgt. Brandon White confirmed that the group told law enforcement that they wanted to leave, and the police assisted them.

"It wasn’t planned. It wasn’t orchestrated. We had a request that they would like to leave the area and so we facilitated,” he said, The Oregonian reported.

Their departure seemed to lower the tension, although the large numbers of police had already kept confrontations to a minimum.

The far-right forces were largely identifiable by their camouflage body armor and helmets, while the far-left antifa groups covered their faces with masks or bandanas.

Concrete barriers, patrolled by baton-wielding police, also helped separate the two sides in a show of force promised by Mayor Ted Wheeler. None of the nearly 1,000 police officers were given the day off.

Wheeler told CNN that police were maintaining "an active, visible presence that so far seems to be keeping a lid on any potential skirmishes."

Police, some on bikes, many wearing helmets and armor, lined or patrolled the main road between the business district and the park to try to keep competing groups apart. Using bullhorns, they frequently warned people not to walk on the streets.

Thousands of people began filing into the area around 11 a.m. PST, many simply standing around, as shown on a livestream from KOIN. One person hoisted a sign that read, "No Trump, No KKK, No Fascist USA!" Another sported a pig's mask with orange hair.

At one point an ad hoc march began in the park, with clumps of activists driving off some individuals by chanting, "Go home, Nazis!"

In some places, individuals faced off with heated, verbal exchanges, with one person in a red "Make America Great Again" hat exchanging words with an African-American man in a red cap.

During some tense moments, a black street-preacher would emerge to defuse arguments. "We're going to surprise America," he told the crowd. "They thought there would be a bloodbath, but we are going to love each other."

At a another point, a small cluster of men in military-style gear, and helmets, accompanied by a man walking a dog and carrying an American flag and joined by at least one woman, were hounded for blocks by hundreds of people shouting for them to leave town. One of the group had been splattered with food.

Police on bicycles eventually arrived to defuse the scene. They were quickly joined by dozens of helmeted officers wielding batons who arrived on vehicles outfitted with outside running boards.

Late Saturday afternoon, Portland Police declared the demonstrations a civil disturbance, more than six hours after they began, and told people to leave the area immediately.

Earlier, President Donald Trump threw a spotlight on the tense confrontation by tweeting that the city is "being watched very closely" and that he hopes the mayor will "do his job."

In response, Wheeler told CNN that he was focused on the community and not tweets from Washington, but added: "Frankly it is not helpful in such a dangerous and volatile situation."

More than two dozen other agencies, including the Oregon State Police and the FBI, planned to help local authorities.

The city's concern was that a far-right rally dubbed "End Domestic Terrorism" could turn into a slugfest after a militant, far-left antifa, or anti-fascist, group vowed to confront the rallygoers they described as "invaders."

In his tweet, Trump echoed the event's theme by noting that "major consideration" is being given to declaring the militant leftist group "antifa" as a terrorist organization.

On the other side, Rose City Antifa, whose activists normally wear masks to remain anonymous, have also said the goal of the far-right was to have antifa declared a domestic terrorist organization.

In Washington, Republican Sens. Ted Cruz of Texas and Bill Cassidy of Louisiana have introduced a congressional resolution calling for anti-fascists to be declared domestic terrorists.

The event, which had not been given a permit, was organized by Biggs and supported by Enrique Tarrio, national head of the Proud Boys, an all-male, far-right group that describes itself as "Western chauvinists."

Some key bridges and roads were closed or blocked off and the city erected a half-mile of concrete barriers along the streets near the waterfront rally area.

Several Starbucks stores closed down for the day after posting signs saying they were shutting down at the "strong encouragement" of police and for the safety of customers. Numerous department stores, computer shops, and other outlets also planned to shutter their doors for the day.

Josh Johnston, owner of Paddy’s Bar and Grill, told KPTV that his staff was bringing in the patio furniture that demonstrators in the past had thrown in the street. “I think it’s unfortunate that people are becoming so polarized and you know the two extreme sides, there just seems to be so much anger that it’s escalating,” he said.

In addition to the Proud Boys, the white nationalist American Guard and the Three Percenters, a far-right militia, have said they will have members in Portland. Hate group watchdogs say the Daily Stormers, a neo-Nazi group, are also expected.

The Oath Keepers, another far-right militia group, said in a statement they were pulling out of the rally because organizers have not done enough to keep white supremacist groups away.

Patriot Prayer’s Joey Gibson, who is not involved in this weekend’s event but organized similar rallies in the past two years that ended in clashes, turned himself in to police Friday on an arrest warrant for felony rioting. He was at a confrontation that broke out on May 1 outside a bar where members of the antifa movement had gathered after a May Day demonstration.

In a video he livestreamed on Facebook, Gibson accused the police of playing politics by arresting him but not the masked demonstrators who beat up conservative blogger Andy Ngo at a June 29 rally that drew national attention to this small, liberal city.

Ngo has not indicated whether he would attend Saturday's rally, but said on Fox News's "The Ingraham Angle" this week that "the whole thing is a powder keg."

A video of the attack on Ngo led the Proud Boys, who have been designated a hate group by the Southern Poverty Law Center, to organize Saturday’s event.

“What I’m saying to everybody who’s listening to this (is) they’re trying to shut you guys up. They want you to not show up in Portland, they want to put fear in your hearts,” Gibson said.

Why Portland? It is viewed by many as an outpost of West Coast liberalism that has been particularly tolerant of free public expression in the past. Some critics argue that the police have not taken tough enough measures to head off clashes.

The presence of Rose City Antifa, one of the country's oldest antifa group, has also been a lure for far-right groups.

"I think they come to Portland because it gives them a platform,” says Wheeler, the mayor, according to The Oregonian. “They know that if they come here conflict is almost guaranteed.”

Portland's feared confrontation Saturday is only the latest in a string of political skirmishes downtown. In June, three people were arrested as protesters and counter-protesters battled during random marches that followed two separate demonstrations.

The exchanges also deteriorated into attacks on police, with some antifa protesters throwing eggs and liquids at police officers, who responded with pepper spray near the Pioneer Courthouse Square.

Crowds eventually dispersed after police declared the gathering a civil disturbance and unlawful assembly.

Three people were treated for injuries at local hospitals, including Andy Ngo, a conservative writer who, The Oregonian reports, appeared to be attacked by antifa forces.

The June rally came almost a year after masked antifa forces threw eggs, water bottles and firecrackers at a march by the right-wing group Patriot Prayer, prompting police to declare a riot and revoke the march permit. Officers also seized knives, clubs and chemical spray from antifa supporters.

Contributing: The Associated Press