The Oregon city was inundated with protesters Saturday night, and police decided to move in, riding horses through the crowd, arresting protesters and deploying what appeared to be tear gas or pepper spray, amateur videos showed.
Two officers were injured during the clashes, the Oregonian reported.
The protesters were acting in defiance of a deadline set by Mayor Sam Adams asking them to vacate the city's Lownsdale and Chapman squares by 12:01 a.m. Sunday morning, according to the Oregonian. Sunday marked the thirty-eighth day of Occupy Portland, according to the group's Web site.
The police were forced to retreat at one point as a wall of demonstrators pushed them across a large open space, one video shows, and protesters remained in both locations as of 7 a.m. Sunday morning, the Oregonian reported.
This has re-galvanized our movement, 25-year-old Portland State University student Madison Dines told the paper. We were evicted and now we're staying.
The paper quoted an estimate that there were as many as 5,000 people in attendance as the deadline came and went, and though it started out peaceful, things turned violent at about 1:30 a.m. when the Mounted Patrol unit arrived and police donned riot gear, the paper reported.
Two police officers were injured, the paper said -- one had his leg cut by a projectile thrown by a crowd member, and the other was hurt by a horse, the paper reported. Cameron Matta, 23, was arrested on suspicion of allegedly throwing the projectile at the police officer, according to the paper.