The action came three days after police began handing out written notices ordering people to remove personal items illegally obstructing the sidewalk and other public "right of ways." The fliers said those who failed to remove belongings could face up to one year in jail and a $999 fine.

Police spokesman Sonny Jackson said several people were arrested for interfering with police officers who removed illegally pitched tents and other gear. Clashes between protesters and police over illegal overnight camping outside the Capitol Building have triggered arrests since early October.

"We totally support the First Amendment rights of these individuals. We just want them to do it in a law abiding manner," Jackson said. "The right of way enforcement is going to definitely be taken seriously. We can't afford for people to be injured, tripped, hurt as they walk through the area."

A trash truck also came through the Civic Center Park sidewalk along Broadway to clear out discarded food and other garbage.

Items such as backpacks and sleeping bags were packed into boxes to be saved so protesters can retrieve them at a later time.

"Don't call us. We'll put a notification through the media as to when you can get those items back. But they'll go through the property bureau and then they will be released to you," Jackson said.

Some protesters blocked a nearby street, which riot police quickly cleared. Police officers also doused a bonfire with a fire extinguisher at about 5:30 p.m.

Jackson said police are seeing more people at the Occupy Denver protests who appear to be anarchists simply bent on causing trouble.

One man arrested by police wore a respirator mask and swim goggles as if he were prepared for tear gas or pepper spray.

Earlier in the afternoon, things turned ugly as protesters marched in Denver for the sixth straight Saturday.

A Michigan woman, whose family was visiting Denver for a wedding, said her mother, who's in her 60s, was punched in the face by a protester when she came to the aid of her husband during a confrontation with marchers.

Lori Kirby told 7NEWS family members were leaving a downtown restaurant with an infant when the street filled with marching protesters, including a man carrying an American flag upside down. Both her father and sister are veterans.

"My dad was just trying to say, 'Look, we're veterans. Why would you disgrace the flag,'" Kirby recalled.

"They came out and started swearing in my dad's face, shoving him," the daughter said. "He's 60-something years old. He's a veteran, OK."

"The guy started saying, 'We'll burn the f---ing flag if we want. It's our right,'" according to Kirby.

Her brother rushed to the aid of his father, who has a heart condition, and some protesters tried to punch the brother, Kirby said.

When her "60-something year old" mother, Janet Kowalczik, tried to intervene, one of the protesters punched her in the face, giving her a black eye and scratched neck, Kirby said.

Then protesters set an American flag on fire in an aluminum roasting pan, and Kirby went up and stomped out the flames.

"That's free speech! That's free speech!" protesters chanted on bullhorns.

Police officers led Kirby away from the crowd.

"If you don't want to be here, go to another country," Kirby said about the protesters when she later spoke with to 7NEWS. "My God, people are fighting for your freedom."

"They have a right to protest and say what they want," Kirby said. "But when you're hurting innocent people for no reason, that's ridiculous."

A Colorado state trooper told 7NEWS a group of protesters attacked a car drving near Broadway and Colfax after sunset, even "ripping the wipers off" the car.

Several protesters yelled at police for using too many officers, inciting violence and incurring even larger staffing costs as a result.

Others called police "Nazis" for "just doing their jobs like the guards in the concentration camps" did during WWII.

One of the organizers told 7NEWS the movement is strong and more than capable of riding out the winter.

"I think we're at a point of no return. I think that people are going to keep on protesting. We don't want anybody injured. We don't want anybody to die. But I don't think that that's going to stop people from fighting for all the things that have gone wrong for so long," said Jennie Hartley.