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 allowed 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 two demonstrations were peaceful. About 150 people marched outside the Quebec provincial agriculture ministry and presented a list of concerns about genetically modified food.

Later, a few hundred women chanted, danced and sang outside the security fence. Dozens of police, some in riot gear, kept a close watch, but there were no confrontations.

A candlelight procession by about 300 people left a local university on Thursday night for the seven-mile walk into town. The planned route avoided the security zone set up by police.

The protesters represent a diverse range of activists — organized labor, human rights organizations, environmental groups and other who say the talks on creating a Western Hemisphere free-trade zone should be in public instead of a locked-in conference center.

A people's summit of groups opposed to the free trade talks called for a hemispheric referendum on the proposal. In its final declaration after three days of meeting and seminars attended by activists from throughout the Americas, the group urged more attention to democracy, human rights, equality, solidarity and the environment.

"These free trade agreements prioritize exports at the expense of the needs of local communities," the declaration read. "We are witnessing the consolidation of economic and legal corporate power at the expense of popular sovereignty."

The security wall, intended to keep the protesters far from the summit venue, survived a lawsuit this week that challenged it on constitutional guarantees of freedom of speech and movement. 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.

Local activists have made the wall a kind of bulletin board for anti-free-trade and anti-U.S. sentiments. Among the slogans spray painted 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. A caravan of several hundred protesters from the United States turned back at the Canadian border in upstate New York when some people were refused entry.

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.