In the most violent Saturday in more than a month of Occupy Denver demonstrations and marches, Denver police fired pepper spray and pepper balls at a crowd of protesters in Civic Center and arrested 20 people.

Two of the protesters were held for felony charges after police said an officer was knocked off his motorcycle and other officers were kicked, as they moved into the park to tear down illegal tents.

The first midafternoon confrontation had police and state troopers shoulder-to-shoulder pushing a group of marchers off the state Capitol steps, which is out-of-bounds to protesters without a permit. Some of the Occupy Denver sympathizers then raced to set up tents in Civic Center, where city officials have allowed ongoing food tables and sleeping bags but not sleeping structures.

Protesters there surged around about eight police officers. Other officers responding to calls for help fired the pepper bullets, which resemble paint balls. One protester filming the scene — one of hundreds of cameras documenting police activity — was knocked out of a tree in the melee.

Five people were arrested in the first conflict, before 3 p.m. Hundreds of officers and SWAT members converged on the park, and Broadway was shut down for hours as police and protesters reached a tense stalemate.

About a dozen of the angriest marchers stood nose-to-nose with police and screamed profanities or anti-Wall Street slogans. Others tried to calm the situation, even while filming.

Just before 6 p.m., with ambulances waiting and police cruisers covering whole blocks around the park, officers donned gas masks and used megaphones to warn protesters that the remaining tents were illegal. Wielding long batons, a few dozen officers pushed into the park and formed a circle around the tents.

University of Colorado student Daniel Ellen tried to jump through a gap to help other protesters he feared were stuck in the tents but was knocked to the ground by police. He stood up and charged at them again, screaming in anger, took a blow to the temple with a baton and was pushed down twice more.

“I support the people here who are unemployed,” said Ellen, who said adrenaline kicked in and he grabbed one of the batons before getting knocked back again. While the crowd surged around the officers, a Hare Krishna group chanted and danced just behind them.

Fifteen people were arrested in the second action, said Lt. Matt Murray, Denver police spokesman. “All we did was take down the structures,” he said. “We’re reacting to what they do. As long as they are legally protesting, we’ll protect their right to do that. The officers today did a great job of showing restraint.”

The 15 later arrests, including two juveniles, were all for misdemeanors, he said. One of those arrested was taken to the hospital.

Murray said Denver’s newly appointed police chief, Robert White of Louisville, Ky., was aware of the action. White, whose appointment is pending City Council approval, was in Denver on Saturday for a news conference.

A Public Works truck parked in the middle of Broadway after the second sweep was quickly crammed with tents, tarps and the tables and food from the “kitchen” area that was a social hub for protesters.

During a noontime march, which was smaller than the previous three Saturdays, as many as 2,000 demonstrators peacefully made their way through downtown Denver.

As the crowd made its way back to Civic Center on Broadway, they veered east and up to the steps of the Capitol. Officers formed a line at the bottom of the west steps.

Some protesters pushed officers, while others joked with them. One person tagged an unmarked patrol car with orange spray paint — scrawling “99%” across the hood and driver-side door.

Protesters toward the front of the crowd started fighting with one another after one protester told another to stop taunting police.

Fewer than 10 officers in riot gear were in the middle of a hive of pushing protesters. Behind them, a man and a woman were face-down in hand restraints. Officers pushed protesters back, only to have them collapse on them again.

More officers were able to move in after several rounds of pepper spray and one round of pepper balls were fired.

Mike Korzen, 25, washed pepper spray out of his eyes with a bottle of water.

“I was standing there with my hands behind my back,” Korzen said.

He said police had been trying to get people out of the surrounding trees.

During the midafternoon stalemate, U.S. Rep. Ed Perlmutter waded into the crowd alone but for a bullhorn, urging protesters to remain as peaceful as they had been during his previous visit. A few in the crowd drowned his words, shouting that it was the cops in assault gear who needed to tone it down, not them.

“Obviously you’re making an impression,” said Perlmutter, the 7th District Democrat. “You’ve got to de-escalate this thing.”

“We want jobs!” a man shouted back. “Democrats won’t get elected anymore!”

Others standing near Perlmutter defended him to the crowd. “He’s the only elected official who bothered to come down here today,” one said.

Demonstrator Bobby Guerrero said that camping is an important part of the protest.

“We’re just trying to hold our ground,” Guerrero said. “We just want our voices to be heard.”

Denver Post staff writer Weston Gentry contributed to this report.