Opposing sides met during an event outside Gresham City Hall where a Black Lives Matter flag is being flown.
A video of people being placed into law enforcement vehicles with no license plates have been shared on social media.
A lawsuit filed on behalf of four Portland protesters said Trump administration officials unleashed "unprecedented, sustained violence and intimidation on the people of Portland."
A riot was declared after some people attacked the Immigration and Customs Enforcement (ICE) building on Southwest Macadam Avenue.
Barr made the comments while speaking at a press conference in Kansas City meant to provide an update for Operation Legend, the Department of Justice-led initiative launched in early July.
"National leadership, frankly, has been caught napping, and so there are other leaders, other organizations who have risen up and who are speaking out," Roland Martin told Newsweek.
"They're not doing the job," Mark Meadows said of the response to Portland protests from local authorities.
Officers used crowd control munitions to disperse the crowd after the windows of the Multnomah County Building were smashed and burning material thrown inside.
The head of the Department of Homeland Security said he immediately terminated a program that monitored journalists who had published leaked DHS documents after the Washington Post ran a July 30 story uncovering the controversial practice.
A group of protesters allegedly knocked a man unconsciousness after he crashed his vehicle following a confrontation.
The incident is one of several violent interactions that took place between protester groups in the Oregon city over the weekend.
According to the event organizer, more than 100 boats took part in the parade on Willamette River in Portland, Oregon, showing support for the president ahead of November's election.
Police in riot gear were seen charging at a line of protesters carrying shields before using batons and crowd control munitions to disperse the crowd.
Protesters were blocked by law enforcement as they tried to make their way to the Portland Police Association, the scene of previous unrest.
In an interview with Newsweek, DHS Acting Seputy Secretary Ken Cuccinelli said believes racial injustice is a problem in the U.S., but that federal officers were right to crack down on "violent agitators."
An Oregon State Police spokesperson said the officers were being moved "back to counties where prosecution of criminal conduct is still a priority."
Students have been calling for Portland State University to disarm its campus police force for several years.
There were 47 cases of shigella infection reported to the Multnomah County Health Department this year.
District Attorney Mike Schmidt announced this week that his office would not pursue charges against most of those arrested as part of the demonstrations.
"We have to isolate those individuals where we can do so safely," Mayor Ted Wheeler said. "We need to arrest them, and we need to hold them accountable."
Portland police officers on Tuesday said that protesters threw "dangerous objects" at them during a rally Monday night, which marked the 74th consecutive night of protests in the city.
I believe Caesar "The No Drama Llama" has an ability to be a bridge between both sides. Protesters in their full PPE want to take pictures with Caesar and federal marshals wearing their camouflage gear have taken selfies with him. People see that calmness he can bring.
Attorney General William Barr said he believes America is facing a "new form of urban guerrilla warfare."
Videos posted to social media showed people adding objects to fuel the fire after a hole was made through the plywood boarding up the building.
"You are creating the B-roll film that will be used in ads nationally to help Donald Trump during his campaign," Portland Mayor Ted Wheeler told prospective demonstrators on Friday.
The clip has been viewed more than 150,000 times since it was posted on Twitter.
The federal government has faced a series of lawsuits over its Portland deployment.
Between July 4 and 31, federal officers suffered a combined total of 277 injuries, DHS Acting Secretary Chad Wolf said.
"Now is the time to accelerate the fundamental preventive measures that we all talk about," Fauci said Thursday.
There are tried and tested ways of reducing the gun violence that plague America's cities. Operation Legend resembles none of them.