Police arrested 20 people and fired pepper spray and pepper balls as they moved to tear down tents set up by Occupy Denver demonstrators on Saturday. Amid angry scenes, two protesters were held on felony charges after police said an officer was knocked off his motorcycle and other officers were kicked.
Patricia Hughes, 38, a nurse who was at the Denver demonstration described the police behaviour as "brutal and outlandish."
She said that police were putting on their riot gear before the demonstration began and that more than 100 officers charged into the crowd after one officer fell while dismantling a tent.
"It's an extraordinary decision that the police in Denver think rubber bullets are an acceptable response to a peaceful protest," she said.
Hughes said the Occupy demonstrators planned to hold a general assembly to discuss their response to the incident and to call for donations of warm clothes and hats which she claimed police had confiscated.
In Portland, about 30 demonstrators were arrested after they marched to the Pearl District, a gentrified former industrial area, early on Sunday. The arrests came after the protesters defied a midnight curfew to leave Jamison Square.
In Nashville, Tennessee, demonstrators defied a curfew near the Capitol building. It was the third consecutive night that they had refused to abide by the police curfew. There were no arrests, but demonstrators had been arrested on previous evenings.
"My heart has been here all along, but the arrests gave me the momentum to come," 61-year-old Vicki Metzgar, the director of a Nashville public schools science and maths initiative, told the Associated Press. "This [plaza] belongs to us, not the politicians."
The demonstrations ended a galvanising week for the Occupy movement after Scott Olsen, a 24-year-old former marine who served in Iraq, was seriously injured by a police projectile during a demonstration in Oakland, California.
Jean Quan, the mayor of Oakland, apologised for the clashes between police and demonstrators on Saturday. In a video statement in which the shouts of protesters rallying outside City Hall could be heard in the background, she said she was "deeply saddened".
The arrests in Denver came as an early snowstorm hit north-eastern cities, leaving two million people without power and contributing to a quiet weekend for protesters in New York and Boston.
The Boston mayor, Thomas Menino, urged activists who have been camping out on a downtown square for weeks to leave for the night because of the weather. Many, however, braved the cold.
In New York on Friday, city authorities took away generators being used by demonstrators to keep warm and power electronic devices.
This article was amended on 31 October 2011. The original described the mayor of Oakland as saying he was deeply saddened. Jean Quan is a woman.