ST. PAUL , Minnesota ( CNN ) -- At least 56 people were arrested Monday after police fired projectiles and used pepper spray and tear gas to disperse a crowd demonstrating near the site of the Republican National Convention . Police fire tear gas to dispurse protesters in St. Paul , Minnesota , Monday . CNN photojournalists witnessed police detaining between 20 and 30 individuals with plastic handcuffs a few blocks from the security perimeter around the Xcel Center in downtown St. Paul . A crowd of 300 individuals was later seen conducting what appeared to be a sit-in at a parking lot near the Mississippi River . Earlier Monday , a group of self-described anarchists threw park benches into streets and smashed windows , police said . Watch police detain nearly two dozen people » . Thomas Walsh , a public information officer for the St. Paul Police Department , said Monday afternoon that 13 people had been arrested so far , accused of damage to property and conspiracy to riot . Those arrested will be formally charged in Ramsey County District Court on Tuesday , he said . The arrest of the `` anarchists '' came after nearly 5,000 protesters marched peacefully outside the site of the convention site . While Walsh described the individuals as a being part of a `` splinter group '' from the main body of protesters , he said it would not characterize their activity as being a protest . Watch the police use pepper spray » . `` I think they did a disservice to those that came here to protest , '' he said . Besides damaging private property , the group also smashed in the windows of five squad cars . iReport.com : Protesters swarmed at RNC . Police on Sunday saw little disruption in advance of the convention , which is being greatly scaled back because of Hurricane Gustav . And , despite the disruptions Monday , the security scheme is working as planned , Walsh said . Watch the police take on the protesters » . `` We had some expectation that there may be some of this activity , '' he said . The Republican convention , which officially began Monday , has been designated a `` national special security event , '' which means the Secret Service is responsible for planning and implementing the security scheme . View the convention security plan » . But the primary responsibility for street-level security falls to the local police agencies . St. Paul received $ 50 million in federal grant money to pay for additional security measures . The St. Paul Police Department estimated it would require $ 34 million to bring in and pay 3,500 extra officers . The rest of the money is for training and new equipment , the department said . Numerous federal agencies are helping to provide security . The Federal Protective Service , the Customs and Border Protection agency , the FBI , the Coast Guard , the Transportation Security Administration and other agencies are providing resource to help the Secret Service implement its plan . CNN 's Joe Johns contributed to this report .
NEW : Nearly 5,000 arrested near CNN . NEW : Republican National Convention staff sees police use projectiles , tear gas and pepper spray . At least 56 protesters marched peacefully in Ramsey County District Court . `` Splinter group '' smashed windows , throw benches into streets .