St. Paul, Minn. - Activists planning protests around the Republican National Convention say they are being targeted in a heavy-handed attempt to chill dissent after police arrested five people, detained dozens of others, and seized computers and protest guides in raids Friday night and Saturday on private homes and the major meeting center.

    The "RNC Welcoming Committee," an organization of dozens of activist groups and individuals from around the country, has been planning demonstrations for over a year at the convention. The largest, which activists said could draw up to 50,000 people, is scheduled for Monday, the opening day of the convention.

    At around 9:15 p.m. Friday, Ramsey County sheriffs and St. Paul police officers kicked in the door of a former theater in St. Paul that the group had rented as a central planning office, said Lisa Fithian, a nonviolence coordinator working with the protesters. They ordered the 50 people inside onto the floor, where they were handcuffed, photographed and asked for identification, then had their possessions searched.

    Police kept at least three laptops, plus schedules and 7,000 "welcoming guides" organizers planned to distribute to people coming to the Twin Cities for demonstrations, Fithian said. Those inside were released within two hours, she said.

    On Saturday, police raided four other homes and arrested five people. They were being held at the Hennepin County jail in Minneapolis Saturday on suspicion of conspiracy to riot, conspiracy to commit civil disorder and conspiracy to damage property.

    "The 'Welcoming Committee' is a criminal enterprise made up of 35 anarchists who are intent on committing criminal acts before and during the Republican National Convention," Ramsey County Sheriff Bob Fletcher said in a statement. "These acts include tactics to blockade and disable delegate buses, breaching venue security and injuring police officers. They have recruited assistance in their criminal conspiracy from other anarchists groups throughout the country."

    Activists who gathered Saturday evening at the Rivertown Events Center, where the Friday night raid occurred, said they were shaken by the raid but not deterred. Some shared stories - and photos - of police arresting and handcuffing other suspected activists around the area.

    "I think (Friday night's raid) was a scare tactic to not go to the big demonstration Monday," said Monica Trinidad, a 22-year-old University of Illinois at Chicago student who was handcuffed outside the center Friday night as she was returning to see what was going on. "But I don't think it's going to work."

    Hal Muskat, a 61-year-old San Franciscan and member of Veterans for Peace, said the arrests might attract even more protesters.

    "It was a tactic to try and take out the leaders," he said. "I know some people don't like to go out in the streets. But when anybody within a 12-hour drive hears about what's going on here, they're going to want to be here with us on Monday."

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    E-mail Joe Garofoli at jgarofoli@sfchronicle.com.