ST. PAUL, Minnesota (CNN) -- St. Paul police fired chemical agents and projectiles into a large crowd of protesters outside the Republican National Convention on Tuesday night.

Police fire chemical agents after some protesters said they would breach a security fence. more photos »

Witnesses said the protesters marched from the grounds of the state Capitol after a concert there ended abruptly.

The protesters were noisy but peaceful as they approached the convention. Once they arrived, a police officer read an order to disperse, CNN reporters on the scene said.

But almost immediately, officers along the exit route opened fire with gas and projectiles. In one instance, a CNN producer said, an officer stepped out of line to hit a young woman with pepper spray as she ran for the exit. See police spray marchers »

Police said officers were trying to scatter protesters who they said \were trying to get past security fences.

Police told the AP that about 2,000 people participated in the anti-poverty march, which lasted about three hours.

Other officers used gas and pepper spray in the path of those attempting to comply with the disperse order, forcing some to stop in their tracks, a CNN crew reported.

The incident comes after almost 300 people were set to be formally charged in Ramsey County District Court on Tuesday after they were arrested during protests Monday at the Republican National Convention, police said.

On Monday, police arrested 283 people after firing projectiles, pepper spray and tear gas to disperse a crowd demonstrating near the convention site, St. Paul Police Department Chief John Harrington said.

Police used plastic handcuffs to detain 20 to 30 of them a few blocks from the security perimeter around the Xcel Energy Center in downtown St. Paul.

St. Paul police said that 120 of the 283 arrested were being held on felony charges. The rest were charged with various misdemeanors. iReport.com: Cops swarm bikers, protesters

A crowd of about 300 people conducted what appeared to be a sit-in in a parking lot near the Mississippi River on Monday. Watch police detain protesters »

Earlier in the day, a group of self-described anarchists threw park benches into streets and smashed windows, police said.

St. Paul police spokesman Thomas Walsh said Monday afternoon that some of those arrested are accused of property damage and conspiracy to riot.

The arrest of the "anarchists" came after almost 5,000 protesters marched peacefully outside the site of the convention. Walsh said they were part of a "splinter group" of the main body of protesters. He said he would not characterize their activity as a protest. Watch police use pepper spray »

"I think they did a disservice to those that came here to protest," he said.

Five police cars were among the property that was damaged, Walsh said.

Harrington said police arrested nine additional people overnight Monday.

Court proceedings were slowed Tuesday when 22 people facing misdemeanor charges refused to give their real names, Dave Gill, a Ramsey County public defender, told The Associated Press. Only two people out of all those arrested completed their initial hearings as of midday, the AP reported.

On Sunday, police saw little disruption ahead of the convention, which was scaled back because of Hurricane Gustav.

Despite Monday's disruptions, the security plan is working, Walsh said.

"We had some expectation that there may be some of this activity," he said.

The Republican convention, which began Monday, has been designated a "national special security event," which means the Secret Service is responsible for planning and implementing security.

But the primary responsibility for street-level security falls to local police agencies. St. Paul received $50 million in federal grant money to pay for additional security. View the convention security plan »

The St. Paul Police Department estimated that it would require $34 million to pay 3,500 extra officers. The remaining money is for training and equipment, the department said.

Numerous federal agencies are helping provide security, including the FBI, the Federal Protective Service, Customs and Border Protection, the Coast Guard and the Transportation Security Administration.

CNN's Steve Turnham, Kevin Myers and Joe Johns contributed to this report.

All About St. Paul (Minnesota) • Republican National Convention • U.S. Secret Service