QUEBEC Police sealed off the heart of old Quebec City on Thursday, creating a heavily guarded security zone to keep protesters and possible violence away from a summit of 34 leaders, including President Bush. Forklifts hoisted concrete blocks topped with wire mesh into busy intersections, and hundreds of police in bulletproof vests stood guard at spots along the 2.3-mile fence encircling meeting sites of the Summit of the Americas. More than 6,000 police officers will patrol the security zone Friday through Sunday to guard against incursion by the expected 10,000 or more protesters. Quebec City residents and demonstrators from around the world watched as the final pieces were dropped into place. Police are letting through only residents with special passes and delegates, journalists and workers accredited for the meeting. Protesters have dubbed the barrier the "Wall of Shame'' and liken to it to the Berlin Wall as a symbol of oppression and division. Thousands of anti-globalization activists have come to this picturesque 17th-century city, and organizers fear the kind of violence that derailed trade talks in Seattle in December 1999. But the first march of the week was peaceful. About 150 people marched Thursday outside the Quebec provincial agriculture ministry and presented a list of concerns about genetically modified food. A minister accepted the document. The protesters represent a diverse range of activists organized labor, human rights organizations, environmental groups and other who say the talks on creating a free-trade zone should be in public instead of a locked-in conference center. "The fence is a symbol of the destruction of our rights,'' said Clara Fogal, a director of the Defense of Canadian Liberty Committee, a human rights group. Her group and others supported a lawsuit challenging the constitutionality of the wall. A judge agreed Wednesday that the wall restricts personal rights, but said it was justified because of the security risks. Police cite concerns of Seattle-like violence to defend the fence, which surrounds several acres of landmarks like the Chateau Frontenac hotel that dominates the old city skyline and the provincial Parliament building. Seven men have been arrested on charges of planning violence at the summit, and police seized military smoke grenades and small explosives. The closest protesters can get to the convention center where the summit is being held is 100 yards across a cemetery, on Rue Saint-Jean. Along the streets, shop windows were covered with plywood or metal screens Thursday in anticipation of unrest. "The whole situation is deplorable. I'm going to keep my kids inside the whole time. I may even leave town,'' said Patricia Hamel, owner of the Collection Lazuli gift shop. To stay open on Friday and Saturday, she said, she would need to hire security guards, and the protests would probably scare away most customers anyway. Local activists have made the wall a kind of bulletin board for anti-free-trade and anti-U.S. sentiments. Among the slogans spraypainted throughout the city are "Bush Go Home,'' "Berlin'' in reference to the wall that divided East and West Germany for decades, and "Viva Cuba'' in support of the only hemispheric country barred from the summit for its lack of democratic elections. Plastic flowers and colorful balloons are attached elsewhere. Protests also are planned far from Quebec City, with marches or blockades threatened in other Canadian and U.S. cities and in Tijuana, Mexico, near the border with California. Cyberprotests also could occur. The Electrohippie Collective says it is targeting Web sites connected with the summit for protest activity most likely a flood of e-mail that would hamper operation of the sites.