These undated photos provided Saturday by the Chicago Police Department shows three men who were arrested accused of making Molotov cocktails with plans to attack President Barack Obama's campaign headquarters. -AP Photos

“The individuals we charged in this investigation are not peaceful protesters. They are domestic terrorists,” state attorney Anita Alvarez told reporters.

“Some of the proposed targets were the campaign headquarters of President Barack Obama and the home of mayor Rahm Emanuel.”Lawyers for the three men arrested in a raid Wednesday night insist that they are innocent and were instead the target of a police “setup” aimed at discrediting the protest movement.

But prosecutors and police said they had plenty of evidence that the “self-proclaimed anarchists” were building Molotov cocktails and planned to wreak havoc during the Nato summit.

They also spoke extensively of plans to attack four police stations -- with one of the men allegedly saying “have you ever seen a cop on fire?” about the plot, Alvarez said.

Fears that demonstrations could turn violent have put Chicago on edge, with some downtown businesses telling office workers to ditch their suits and ties and dress down to avoid being hassled or targeted on the streets.

Police and protest organizers have vowed that there will be no repeat of the trouble that erupted at G20 summits in London and Toronto or the riots that scarred Chicago during the 1968 Democratic National Convention.

Police superintendent Garry McCarthy said there are “no imminent threats”to the Nato summit but declined to comment if more arrests would be made in connection with the apparent plot.

“We have not completed this investigation,” he told reporters. “This is a step we had to take to make these arrests based on the danger these guys presented.”McCarthy also said the men arrested did not represent the protest movement.

“I'd like to separate this from the peaceful yet raucous protests we've had,” he added.

“We are going to protect people's first amendment rights to free speech while at the same time being intolerant of criminal behavior.”Several street protests held this week were peaceful, and most of the 14 people arrested were engaged in acts of civil disobedience such as refusing to leave the building housing Obama's campaign headquarters.

The three men charged were Brian Church, 22, of Fort Lauderdale, Florida; Jared Chase, 27, of Keene, New Hampshire; and Brent Betterly, 24, of Massachusetts.