PORTLAND, Ore. – Twenty-six people were arrested overnight after a peaceful Donald Trump protest turned into a riot in Portland Thursday night into early Friday morning.

It was the third straight night people took to the streets to voice their opposition to Trump's election. At around 8:30 p.m., Portland police, who took a hands-off approach the previous two nights, tweeted the protest was considered a riot "due to extensive criminal and dangerous behavior."

The crowd remained mostly peaceful until demonstrators met with an anarchist group that scheduled an 8 p.m. rally at Holladay City Park. Police estimated there were as many as 4,000 protesters.

Multiple acts of vandalism then took place in Northeast Portland. Protesters tagged buildings, kicked cars, shattered an office building window and knocked out power.

Protesters also vandalized 19 vehicles at Toyota of Portland on Northeast Broadway Street.

"They started throwing bricks through windshields. The cars are totaled," a worker told KGW. "I believe in peaceful protest but this is ridiculous. We're a nation that needs to come together and heal."

Protesters tried to take over Interstate 5, as they had the previous two nights, but police blocked them from entering the freeway.

To get back to the westside, protesters crossed the Broadway Bridge then walked through the Pearl, where mayhem broke out as protesters smashed windows with baseball bats while other protesters tried to stop the destructive actions.

“What you saw was anarchist individuals," Sgt. Pete Simpson of Portland police said of the people who committed the criminal acts.

Shortly before 10 p.m., police in riot gear converged on the march and instructed those who want to protest peacefully to head to Pioneer Courthouse Square, where the protest started at about 5 p.m. Some protesters were detained, however there did not appear to be a mass arrest.

Protesters returned to Pioneer Courthouse Square before heading south on Southwest 6th Avenue, when at about 11:30 p.m., they were stopped by police in riot gear at the intersection with Yamhill Street. Police set off smoke bombs and flash bangs, and most of the crowd of about 1,500 protesters dispersed. Police detained several people at that time.

The protest began as a peaceful demonstration by a newly formed group called Portland’s Resistance. From the rally at Pioneer Square, the crowd of thousands of people marched east on the Hawthorne Bridge, blocking traffic and stranding drivers.

Photos: Trump protests in Portland

The Oregon Department of Transportation briefly closed freeways in the Portland area. Interstate 5 was closed between the Fremont and Marquam bridges, and westbound I-84 was closed at Lloyd Boulevard.

Witnesses said one woman who was stuck in traffic got out of her car and tried to throw bleach at some of the protesters, who knocked her to the ground.

Protesters then headed north on Southeast Grand Avenue, as they did Wednesday night. .

One woman, who claimed to be in an emergency, tried to get around the crowd in her vehicle and had her windshield smashed, witnesses told KGW's Mike Benner.

TriMet MAX and bus lines were delayed throughout the night. Some MAX stations, including two at Pioneer Square and two at PSU, closed early for safety reasons, according to TriMet spokeswoman Roberta Altstadt.

President-elect Donald Trump tweeted about the protests across the country, calling them professional protesters incited by the media.

On Wednesday night, protesters marched through downtown Portland and onto freeways to protest Trump’s election. The crowd grew to more than 2,000 people and did not stop marching until early Thursday morning.

The demonstration was mostly peaceful, but there were scattered acts of vandalism and small fires. Police arrested one man who they said threw a Molotov cocktail into a fire. No one was injured by the explosive.

Portland Mayor Charlie Hales declined an on-camera interview Thursday, but said in a written statement that “vandalism, and destruction of public and private property in our city cannot, and will not be tolerated.”

KGW's Dave Northfield and Associated Press contributed to this story.