Bolstered by emergency help from the Minnesota National Guard, police in St. Paul arrested 284 people Monday after outbreaks of violence and road obstructions linked to rogue bands of demonstrators among an otherwise peaceful throng estimated at 10,000 people.

The demonstrations, on a steamy first day of the Republican National Convention, began with block after block of marchers -- far fewer than the 50,000 some had predicted -- chanting and peacefully waving signs on downtown St. Paul's narrow streets. As the day wore on, the carnival atmosphere turned ugly.

Before most of the demonstrators had finished their march, a few hundred protesters splintered off and became confrontational and sometimes violent. Some smashed windows at Macy's and a downtown bank building. Others challenged police by blocking roads.

Late Monday, authorities said 130 of the 284 people arrested may face felony charges. Dozens were pepper-sprayed and tear-gassed. One police officer was punched in the back, and another suffered from heat exhaustion. St. Paul emergency rooms reported nine minor injuries and several heat-related cases.

Hundreds of police officers, sweltering in heavy riot gear, swept in to block streets and protect delegate buses. About 3 p.m., St. Paul police requested help from 150 National Guard troops.

St. Paul Mayor Chris Coleman said officers showed restraint as a small number of law-breaking demonstrators marred an otherwise peaceful day of free speech.

"Their efforts were nothing short of heroic," Coleman said. "They did not fail. They did not take the bait."

But observers from the National Lawyers Guild took issue with police action.

"We think it's unconscionable. We think it's out of control," said Gina Berglund, an attorney and legal observer coordinator for the guild's Minnesota chapter. "The response by the police was completely out of proportion with what they were faced with."

St. Paul Police Chief John Harrington said the troublemakers came from a half-dozen loosely organized groups totaling up to 180 people, a small fraction of Monday's turnout.

Some delegates attacked

Members of the Connecticut and Alabama delegations reported being attacked at one point by protesters. Connecticut delegate Rob Simmons told KMSP-TV that protesters tried to rip the credentials off delegates' necks and sprayed them with a toxic substance that burned their eyes. One 80-year-old delegate was treated for injuries, and several others had to rinse their eyes and clothing.

Also, retired Alabama Supreme Court Judge Terry Butts said about 100 protesters approached a delegation bus and one threw a brick through a window. Butts said the bus driver suffered cuts.

A cross-section of dissent

Protesters had come from across the state and the country for what was expected to be the week's largest demonstration. They marched after a noon rally at the State Capitol, snaking down a route that circled in front of the Xcel Energy Center as delegates arrived for a session cut short by Hurricane Gustav.

Cu Nyugen, a Vietnamese native who lives in Minneapolis, brought his 12-year-old daughter, Mai, on the eve of her first day of sixth grade. "It's important for the younger generation to see and learn about different points of view," Nyugen said.

Marie Williams, 77, of Minneapolis, carried a "Dissent Is Patriotic" placard. "I started coming to protests with Paul Wellstone," she said.

Some were disappointed by the turnout, wondering if the 90-degree heat, aggressive police and President Bush's cancellation thinned the crowd.

"I'm disappointed -- this is far too few people," said Lennie Major, a teacher from Mounds View. "We needed 10 times this many to make an impact; this will only be a blip."

Escalating violence

Harrington said the first illegal salvo happened about 11 a.m., when a Dumpster was shoved into an occupied squad car on W. 7th Street. "I'm not sure how anyone can say that's protest," Harrington said.

The peaceful mood started to change after 1:30 p.m., when several groups broke off and began resisting police. The biggest showdown occurred about 5:30 p.m., when police in riot gear cornered about 80 protesters near the Mississippi River below the Minnesota Science Museum. Daniel Streltz, a freelance photographer, said the protesters sat down when police ordered them to disperse. By early evening, police had arrested most of them.

About 3 p.m., about 250 people locked arms to block delegate buses near Robert Street and Kellogg Boulevard. They were in a standoff with 100 police officers, and authorities warned them to disperse. Minutes later, when the group refused to move, officers tossed in a dozen tear-gas canisters, prompting the crowd to retreat.

Some demonstrators then attempted to line the street with obstacles. Witnesses said police also used concussion grenades and smoke bombs.

"Most of [the demonstrators] were pretty good," said CarolLee Folsom, a bystander who used to work for the Ramsey County Sheriff's Office. "But you don't know what any of these people are going to do. And they warned them, so anybody that wanted to get out could have gotten out."

Demonstrator Andrew Sigmundik, 18, disagreed, saying that the police went overboard and that he witnessed "one guy in a wheelchair getting Maced and some other people getting hit by police batons.

"Nobody was trying to cause destruction or violence," he said. "The idea was to just block the streets. We were just trying to disrupt the delegation, and I think we succeeded."

At about 2 p.m., protesters dropped bent nails into the intersection at 6th and Wacouta Streets. A group of more than 200 tossed garbage cans and newspaper kiosks into the road. A few marchers broke off and threw objects, shattering three windows in a bank building at 4th and Minnesota Streets.

Others continued up 6th, pursued by more than a dozen slow-moving police cars. A few officers walked in front of the cars, clearing the barriers the marchers had thrown in the street. By the time they reached 6th and Cedar, many of the marchers began to disperse. Some smashed three windows at Macy's. One person jumped up and down a few times on the roof of a parked police car before breaking its windows.

An alternative broadcaster, "Democracy Now" host Amy Goodman, was among an estimated 40 people arrested about 5 p.m. near the corner of 8th and Jackson. She was arrested as she tried to prevent the arrests of two colleagues, a producer for her show said.

Associated Press photographer Matt Rourke also was arrested when he was swept up with a group of protesters. He was released without charges.

Staff writers Randy Furst, Anthony Lonetree, Heron Marquez Estrada, Maria Elena Baca, Tony Kennedy, Paul McEnroe, H.J,. Cummins, Rodrigo Zamith, Pat Pheifer, Allie Shah, Richard Meryhew, Kevin Giles, Thomas Lee, David Shaffer, Jean Hopfensperger and Pam Louwagie contributed to this report, along with the Associated Press.