CHICAGO (AP) -- Thousands of nurses and other protesters began gathering at a downtown Chicago plaza Friday to demand a "Robin Hood" tax on banks' financial transactions, the largest protest yet ahead of a two-day NATO summit that is expected to draw even larger demonstrations.
National Nurses United officials expect about 2,000 nurses to attend Friday's rally to call for the tax to offset cuts in social services, education and health care. They were joined by members of the Occupy movement, unions and veterans.
City officials say the event could draw more than 5,000 people because of a performance by former Rage Against the Machine guitarist Tom Morello, an activist who has played at many Occupy events.
Meanwhile, lawyers for NATO summit protesters said police on Friday morning released four of nine activists arrested Wednesday on accusations that they had or planned to make Molotov cocktails.
The lawyers said police, with their guns drawn, raided an apartment building where activists were staying and arrested nine people. The Chicago chapter of the National Lawyers Guild said officers broke down doors in the building in the South Side Bridgeport neighborhood and produced no warrants.
"The nine have absolutely no idea what they're being charged with because they were not engaged in any criminal activity at all," said guild attorney Sarah Gelsomino. "They're really very confused and very frightened."
The Chicago Police Department refused to comment.
Many office buildings in the usually bustling Loop business district were closed after workers were warned to stay home because of heightened security, snarled transportation and the possibility of unruly protests.
Chicago was originally going to host the G-8 economic summit, too, and the nurses' rally was initially intended to coincide with that. But the G-8 summit was moved to Camp David, Md.
Midwest Director Jan Rodolfo said the nurses decided to go forward with the rally in the hope that their message would reach a worldwide audience.
"What we really hope for is a large, festive, hopeful, constructive tone regarding the Robin Hood tax and that everyone in attendance feels like they're part of a moment in history," Rodolfo said. She said the movement has much more momentum in other countries and "we're hoping to put it on the map" in the U.S.
The nurses and their supporters dressed in red shirts and wore green felt Robin Hood caps with red feathers.
Other small protests, including one targeting climate change, are also planned.
Shawmaf Khubba, a student at Montclair State University in New Jersey, took a 14-hour bus ride on Thursday with 40 others to join the Chicago protests. He said he wanted to raise awareness and tough questions about what he called NATO's unwarranted military aggression around the world.
"NATO is a strong arm of the U.S. that gives an excuse to go everywhere around the world," he said before Friday's rally. "I'm here because I care about what happens to people around the world."
Scattered protests over the past week have been relatively small, including a march through the "Magnificent Mile" shopping district that drew about 100 people Thursday.
But the much larger nurses' rally will mark a ramp-up to Sunday's anti-NATO march by underscoring that money spent fighting wars means less money for health care, education and other social programs, said Andy Thayer, an organizer of the anti-NATO march. His group -- Coalition Against the NATO/G8 War & Poverty Agenda -- has been working to draw those connections ever since President Barack Obama moved the G-8 summit, potentially dampening enthusiasm for a Chicago demonstration.
"I think it's really going to be big ... with the nurses," Thayer said. "That is going to be the 99 percent staking itself against the 1 percent, drawing the connections between the war abroad and the war on working people here at home.
"They are the front-line caregivers ... and the nurses, to their credit, understand the connections between NATO, G-8 and the deplorable state of health care in our country and are speaking out about it."
Estimates of how many might show up Sunday have varied widely, from a couple of thousand to more than 10,000. Busloads of demonstrators from around the country have begun arriving in Chicago, though some who had planned to come, including from the Occupy movement, have said they're staying home or going to an area near Camp David instead.
Police and the Secret Service have taken no chances, as heads of state from 50 countries begin arriving for the NATO summit, where leaders will discuss the war in Afghanistan and European missile defense.
Security is high on trains. Barricades and fences have been erected around landmark buildings. Streets are being closed. And world-class museums are shutting down.
Chicago Police Superintendent Garry McCarthy said Thursday that the protesters so far "have been very well behaved." He said he did not anticipate that the tenor of Friday's rally would be different, but that if it is, "We are going to carry through with what we said we were going to do. We're going to facilitate the rights of these individuals while preventing criminal actions."
Associated Press writers Ryan J. Foley and Jason Keyser contributed to this report.