Police accused the leaders of several prominent protest training groups today of orchestrating property damage and violence during the just-ended Republican National Convention and in other cities around the country.

A leader of the Berkeley, Calif.-based Ruckus Society, who is being held on $1 million bail, is among as many as six prominent activists arrested this week during sometimes-violent protests around the city.

"There's a cadre, if you will, of criminal conspirators who are about the business of planning conspiracies to go in and cause mayhem and cause property damage and cause violence in major cities in America that have large conventions or large numbers of people coming in for one reason or another," Police Commissioner John Timoney said today.

As proof, police presented evidence and photographs of items Timoney said were intended to hurt officers during the convention. Among the items displayed were gasoline-soaked rags tied to chains that police said were similar to those used by protesters in Seattle to light on fire and fling over a crowd.

"The events of this week did not happen in a vacuum. We do have precedents in Seattle and in Washington," Timoney said.

Activists dismissed the accusations.

"There's no way for one organization or one individual to be accountable for the actions of everyone else," said Celia Alario, one of dozens of people with the Ruckus Society who helped train demonstrators before the convention.

In addition to the Ruckus Society, police have singled out the leaders of Philadelphia ACT UP, the nation's largest chapter of the national AIDS advocacy group, and of Philadelphia Direct Action Group, an affiliate of the Asheville, N.C.-based Direct Action Network.

The accusations are surprising because these groups have been acclaimed for inspiring nonviolent activism that has resulted in large, mostly peaceful demonstrations in the past year.

However, the two largest demonstrations--in Seattle last fall, and Washington, D.C., in April--were marred by hundreds of arrests and property damage. Philadelphia ACT UP, Ruckus and the Direct Action Network also were involved in training and organizing in Seattle and Washington.

"We thought these are not bad people. They're not going to engage in anything violent. But their actions belie their words," Deputy Commissioner Robert Mitchell said.

Police did not name the activist leaders singled out as the lead organizers. However, police confirmed that the leaders are facing the most serious charges and have been assigned the highest bails.

John Sellers, 33, a leader of the Ruckus Society, was being held on $1 million bail for misdemeanors including conspiracy, reckless endangerment and related charges.

Terrence McGuckin, a leader of Philadelphia ACT UP, also was being held on $500,000 bail for numerous misdemeanors. Defense lawyer Lawrence Krasner said Kate Sorensen, 34, a leader of the Philadelphia Direct Action Group, was in custody and expected to face charges similar to those against Sellers and McGuckin.

Two men accused of felony assault on an officer, including 20-year-old Darby Landy, who is charged with hitting the commissioner with a bicycle, were each charged with felony assault on an officer and being held on $500,000 and $450,000 bail.

Police said 390 people have been arrested since Saturday, including 39 charged with felonies. More than 300 people were arrested Tuesday during brawls with police and several traffic-blocking demonstrations.

Krasner, who represents 10 jailed activists, said many of the protesters were held on unreasonably high bail to keep them in jail until the convention ended Thursday night.

"It's an unconscionable, ridiculous bail and completely off the map from the norm," Krasner said. "This is a desperate effort to systematically punish these people without a trial, to lock them up, keep them off the streets."