DENVER -- Tuesday started the same way Monday ended -- with tension between police and protesters. At least two people were arrested Tuesday morning on the streets right outside the Denver City and County building.

The clash Tuesday lasted about an hour. Protesters called the choice between Obama and McCain, no choice at all.

Riot police maced unruly crowds gathering in front of the Denver City and County Building Monday evening on the first night of the Democratic National Convention.

It's believed to be the first time police used any force against protesters.

Authorities said police were trying to disperse a crowd of about 300 that had disrupted traffic near Civic Center Park, which is about a mile away from the main convention site -- the Pepsi Center.

The demonstrators, many of whom dawned bandanas over their faces, began chanting, "Our streets, our streets," around 7 p.m.

As police with shields and clubs moved the crowd back to the sidewalk, the group of protesters began to run north toward the Wellington Webb building.

Officers put on gas masks while forming a line in front of demonstrators.

One protester stood in the center of the 15th St. and made peace signs with his hands.

Officers on horseback joined other police who responded on SWAT vehicles.

Police led at least two people away as the crowd chanted "Let them go!"

One protester who left the scene said he'd been hit with paint ball-type bullets.

"We were all marching; no one did anything," said Eric Finch, who told 7NEWS he was from out of state and not a part of any group.

Some of the protesters threw bags containing a colored liquid at police.

The disturbance resulted in about 100 arrests, on charges of failure to obey a lawful order, obstructing a public roadway and interference, Jefferson County sheriff's officials said.

Three hours after the confrontation, officers continued to line sidewalks in the area in an attempt to get loiterers to leave.

"It would be nice if we could get people to disperse, but they're not committing a crime," said Jacki Kelley, a sheriff's office spokeswoman.

Earlier Monday, protesters wearing jail-style orange jumpsuits and black hoods over their heads marched along a downtown pedestrian mall chanting "Stop the torture, stop the war."

The protesters, estimated at several hundred, were at a rally at Civic Center Park near the state Capitol when they began pouring down the mall at midday, hours before the convention started.

Some were dressed like inmates at the infamous Abu Graib prison in Iraq.

The sidewalks along the mall were crowded and protesters got off the sidewalk and marched in the street, where free shuttle buses run, for a few blocks. Police asked them to get back on the sidewalk and they complied.

Later in the afternoon, about a half dozen men holding signs opposing homosexuality attracted a steady stream of people wanting to argue with them. The demonstrators were surrounded by police and the clump of people arguing with the men and taking photos temporarily prevented mall buses from passing.

Denver police said one man was arrested there after he allegedly tried to prevent officers from contacting another counter-protester. Police spokesman Sonny Jackson said the counter-protester, who got away, had a bottle with a liquid inside that raised their suspicions. Officers at the scene had a clear bottle with a colored liquid inside a plastic bag.

At least eight other people were arrested across the city on Monday, including five detained about a mile southeast of the state Capitol. Four faced charges of disobeying a lawful order, two faced a trespassing charge, and two faced false information charges.

The march from Civic Center to the old federal court house, organized by Recreate 68, was against the U.S. detention of people protesters called political prisoners, including American Indian activist Leonard Peltier and five Cuban men who are behind bars in the United States for espionage. Peltier is serving a life sentence for killing two FBI agents during a 1975 standoff on the Pine Ridge Indian Reservation in South Dakota. The Cubans say they were monitoring terrorist groups in Miami they feared could attack Cuba.

When they arrived at the old federal courthouse, the crowd listened to a recording by Mumia Abu-Jamal, in prison for killing a police officer 27 years ago in Philadelphia. Activists in the U.S. and Europe have rallied in support of the former Black Panther's claims that he is the victim of a racist criminal justice system.

"Here, democracy is on life support," Abu-Jamal said on the recording.

An appeals court in March upheld Abu-Jamal's murder conviction but said jury instructions in the death penalty phase of his trial were flawed. It said he must get a new sentencing hearing or be sentenced to life in prison.

Speaker Pam Africa, of Philadelphia's MOVE Organization, let loose a string of profanities, lashing out at police and government. People in the crowd pumped their fists in the air and cheered. A couple dozen federal officers stood at ease in a corner while she accused them of being traitors for working for the government.

An officer shook his head no when asked if anyone in the group wanted to respond.

Earlier, a small group of protesters marched to the demonstration zone outside the Pepsi Center, where the convention is being held, complaining they are being treated like political prisoners.

It was the first time members of the Recreate 68 Alliance had visited the fenced-off zone, and they vowed not to return because they oppose the limits on where they can demonstrate.

Protesters derisively call the 47,000 - square foot zone the "Freedom Cage." It's separated from the parking lot around the convention hall by metal fences atop concrete barriers.

They complained it is about 700 feet from the Pepsi Center entrance. Secret Service spokesman Malcolm Wiley said the entrance is 770 feet from the demonstration zone, but the distance is irrelevant because protesters will be within sight and sound of the delegates, which is required by law.

The city, which won a federal lawsuit challenging the demonstration zone and other security measures, has emphasized that a pathway delegates can take to the area is about 200 feet from the fenced-in area. Sue Cobb, Mayor John Hickenlooper's spokeswoman, said delegates could get within 8 feet of protesters in the area.

"We're being treated by the city of Denver and the Secret Service like political prisoners, like pariahs," said Recreate 68 organizer Mark Cohen.

Holly Heiman, 40, of Green Mountain Falls, was among those who walked from the pedestrian mall to the demonstration zone. She said she wanted to show her opposition to what she believes is an oppressive government that won't change no matter who is elected.

"It's kind of shocking there aren't more people" protesting, Heiman said.

A signup sheet for speakers at the protest zone had a number of fake signatures and comments such as, "J. Stalin -- This is awesome" and "G. Washington -- You can't cage freedom."

At one point about 30 lost volunteers, wearing credentials and green T-shirts, wandered into the protest area in search of the Pepsi Center. They refused the protesters' literature.