Three men face terrorism-related and explosives charges in connection with a plot that allegedly included an attack on President Obama's campaign headquarters, police stations and squad cars, prosecutors said Saturday.

Officials said a raid of the South Side apartment in which the men were staying uncovered petroleum bombs known as Molotov cocktails, bows and arrows, throwing stars and gas masks.

Thousands of people, including protesters, have been in Chicago for days ahead of the two-day NATO Summit that starts Sunday.

"These individuals are domestic terrorists who came to Chicago with an anarchist agenda to harm police officers, intimidate citizens and to attack their politically motivated targets," said Anita Alvarez, a prosecutor with the Cook County State's Attorney's Office.

Officials said undercover police infiltrated the group and broke the case after the men allegedly were overheard discussing violence.

The men were arrested Wednesday and have been identified as Brian Church, 20, of Fort Lauderdale, Fla., Brent Vincent Betterly, 24, of Oakland Park, Fla., and Jared Chase, 24, of Keene, N.H.

They are charged with providing material support for terrorism, conspiracy to commit terrorism and possession of explosives.

Defense attorneys told a judge that undercover police are the ones who brought the Molotov cocktails and that their clients had been entrapped.

The men were each being held on $1.5 million bond.

They apparently came to Chicago late last month to take part in May Day protests. Six others arrested Wednesday in the raid were released Friday without being charged.

Chicago police Lt. Kenneth Stoppa declined to elaborate on the case beyond confirming the charges against the three who were still in custody.

Church's lawyer Michael Deutsch called the case "entrapment or even worse than entrapment."

"There was (beer) home brewing equipment at the house," he said. "There was no attempt to create any criminal attack, had no intention for any violent act."

Deutsch implied police supplied the bomb-making materials and suggested how the three men should act to "make it seem like people are under attack."

"We know that there were two police informants who infiltrated the group, and we believe they're the ones who provoked this and they're the ones who had the illegal activity and the illegal materials," he added.

Activist Bill Vassilakis, who said he let the men stay in his apartment, described Betterly as an industrial electrician who had volunteered to help wire service at The Plant, a former meat packing facility that has been turned into a food incubator with the city's backing.

Vassilakis said he thought the charges were unwarranted.

"All I can say about that is, if you knew Brent, you would find that to be the most ridiculous thing you've ever heard," he said. "He was the most stand-up guy that was staying with me. He and the other guys had done nothing but volunteer their time and energy."

The Associated Press contributed to this report.