A minor confrontation between police and protesters Thursday did little to dispel the overall impression of calm in this city's streets during the Democratic National Convention this week.

A group of about 200 antiwar demonstrators who had marched from Copley Square to the security perimeter around FleetCenter, where the convention is being held, burned effigies of Democratic nominee John F. Kerry and President Bush.

Pushing and shoving began after heavily padded riot police deployed in front of the demonstrators, while another set of officers approached from behind the pack. Police made three arrests. One person was charged with assaulting an officer, one with disorderly conduct and another for possession of what Boston Police Superintendent Robert Dunford called an accelerant.

"I was trying to help some officers get out of the pack, and I got sucker-punched in the back of the head," Dunford said.

Protesters, one of whom emerged from the melee with a welt on his lip and over his left eye, said that the police had been the aggressors. "We were engaged in harmless, nonviolent street theater," said Charles Shaw, an organizer for the Green Party, which helped lead the march. "There is not an aggressive person among us. Nobody wants to get hit."

The Thursday incident was the only significant clash during four days of tepid demonstrations. Though they demonstrated over causes as diverse as the persecution of Chinese Buddhists and the development of fossil fuels, many protesters said that the common denominator among them was opposition to the Iraq war.

But as speaker after speaker at each day's rallies railed against the Bush administration, they acknowledged some ambivalence about protesting against a Democratic Party that many clearly viewed as the lesser of two evils.

Tim Kaldos, 20, a George Washington University student who is registered to vote in Massachusetts, railed against both political parties at a Copley Square rally. But he said that if he lived in a swing state, he would vote for Kerry. "I wouldn't be happy about it, but I want Bush out," he said.

Boston police said they made six convention-related arrests all week.

Some protesters were undoubtedly deterred by the thousands of uniformed police, Secret Service agents and National Guard troops who gave downtown Boston the look and feel of a military installation.

"It reminds me of 'home sweet home,' " said Marc Khoury, 33, an engineer who was born in Beirut, as he took cover behind a car Thursday while bomb squad units detonated a cardboard box found on a park bench. They found nothing dangerous in it.

Protesters said they were discouraged by a demonstration area established by security officials, a stockade of barbed wire and concrete and metal fencing that a federal judge referred to as "offensive to the spirit of the First Amendment," though he decided to leave it in place. It was virtually empty all week.

Some bystanders were caught up in the effort to ensure the safety of the convention.

On Monday, Boston College student Sundeep Sahni, 21, and two friends were walking around and taking photographs on the campus near where some Secret Service agents were being housed. College police and three Secret Service agents arrived and interviewed the trio separately from 6 p.m. until after midnight, when they were released.

"I am furious and more than a little scared," said Sahni, who is an Indian citizen and was released after he signed a form that gave agents access to his psychiatric records. "I think they just basically profiled me because I wear a turban."

Secret Service spokeswoman Ann Roman said agents "followed standard procedure." "There is nothing discriminatory at all about who we interview," she added. "It had to do with their behavior."

Also saying that they have been hurt by the tight security were several local businesses, including restaurants across the city that reported a decline in customers of as much as 50 percent.

Mayor Thomas M. Menino (D) said the economic results, overall, were mixed. "Some businesses aren't doing well," he said. "But others have been booked solid all week."

Boston police officers arrest a demonstrator amid a large group outside the designated protest area near the convention site. A protester burns an American flag and effigies of President Bush and Sen. John F. Kerry on the Democratic convention's final day in a city that remained mostly calm.