PITTSBURGH - Thousands of demonstrators pledging nonviolence banged drums, danced and held signs advocating everything from human rights to ending war during a march through the city where Group of 20 world leaders were meeting.

Police lined the route in front of the marchers, which included a couple dozen anarchists. Their signs included peace signs and one that read, "No bailout no capitalism."

The demonstrators in the so-called People's March were demanding solutions to environmental and economic crises they believe were created by the G-20, said Pete Shell, a protest organizer. Leaders of those countries and the European Union were meeting downtown, a few blocks from where the march was expected to pass by.

The demonstration was sponsored by The Thomas Merton Center, a Pittsburgh peace organization, and bolstered by smaller "feeder marches." The group planned a mid-march rally near a local government building and then another one in the late afternoon.

The march had a city permit and organizers pledged to keep it nonviolent.

On Thursday afternoon, a march without a permit ended with clashes between police and anarchists.

Police declared the Thursday march illegal almost as soon as it began. Small bands of anarchists responded to officers' overwhelming show of force by rolling huge metal trash bins, throwing rocks and breaking windows. Police fired bean bags and canisters of pepper spray and smoke.

Later that night, hundreds of officers surrounded what was mostly a large gathering of University of Pittsburgh students in the city's Oakland neighborhood. The area was adjacent to where G-20 participants opened the summit, but leaders were long gone by the time police declared the gathering illegal and fired canisters of pepper spray and smoke.

In all, several businesses were damaged Thursday and nearly 70 people were arrested on charges including failure to disperse and obstructing traffic. Four face more serious charges of aggravated assault, and two of those are also charged with inciting a riot, according to a Pittsburgh police news release.

People gathering at the starting point of Friday's march shut down traffic for themselves and began the event with folk singers and chanting.

Joshua Nichols, 24, of Telluride, Colo., drove 24 hours to participate. He described himself as a migrant who shovels snow in winter, cleans houses, works on an organic farm and teaches preschool in the summer.

"I am here because I think the G-20 is in part an organization among others that leads to the subjugation of people all over the world," he said. "We need to stand up and say that we're going to put an end to this or it's going to get ugly."

Nichols was accompanied by Lisbet Rattenborg, 23, who is originally from Pittsburgh but now lives in Colorado Springs, Colo.

"I'm here to protest the idea that a few countries can determine the economy for the world, the economic path for the world," said Rattenborg, an intern at Pikes Peak Justice and Peace Commission, an activist group that advocates for human rights, nonviolent conflict resolution and other issues.

Ed Collnan, 62, of Munhall, Pa., came to demand a single-payer health care plan and an end to what he called the "cancer of the insurance system."

Fifteen-year-old Rosi Lowe, a student from Pittsburgh, was in the crowd with a classmate for a school project on the G-20 and had formed a conclusion: "I feel like it's real exclusive and doesn't represent the entire world."