to "punish" them for participating in or being near an anti-police brutality protest after the Group of 20 summit ended in the city last year, the American Civil Liberties Union said in a lawsuit.

The ACLU filed a 42-page federal lawsuit Tuesday alleging police created most of the problems themselves by surrounding about 100 people with officers in riot gear and then ordering them to disperse. Many who tried to leave couldn't and were instead pingponged between groups of advancing police, the ACLU said. Five people not even at the protest were arrested blocks away, the ACLU contends.

"It appears that these police were simply looking for anybody who was young and maybe looked like a demonstrator and then rounded them up," Witold "Vic" Walczak, the ACLU's legal director in Pennsylvania, said at a news conference Tuesday.

The ACLU announced the lawsuit at a plaza near the University of Pittsburgh campus where the protest was staged on Sept. 25, 2009.

"When people see video of peaceful demonstrations in places like Russia and Iran where the police all of a sudden declare the assembly to be unlawful and then come in and arrest everybody ... we recoil in horror and say, 'It's just free speech, it's just peaceful demonstrations. Thank goodness that can't and doesn't happen in this country,'" Walczak said.

"Well, I'm sorry to advise you that in fact it does happen in this country and it did happen in the city of Pittsburgh."

Pittsburgh police spokeswoman Diane Richard relayed a copy of the lawsuit to the city's law department, which did not immediately comment on it. An attorney for the Fraternal Order of Police, which typically represents individual officers in such lawsuits, did not immediately comment on the suit.

The lawsuit says police Chief Nate Harper and Deputy Chief Paul Donaldson sent police to declare the gathering illegal after seeing a protest advertisement that disparaged police with an expletive.

"Instead of providing a way for people to comply with the dispersal order, police funneled everyone onto the lawns of the University of Pittsburgh's Cathedral of Learning," the lawsuit said. Police then surrounded about 100 people, made them lie down, handcuffed them and "falsely charged them with failure to disperse and disorderly conduct," the lawsuit said.

The suit targets the city, Harper, Donaldson and 15 officers identified as those who arrested the plaintiffs, all of whom were held by police for six to 20 hours, the lawsuit contends.

The lawsuit asks a federal judge to declare that the plaintiffs' constitutional rights were violated and to award damages for false arrest and emotional distress.

It also asks the judge to declare Pennsylvania's "failure to disperse" statute unconstitutional. The law allows officers to declare an assembly unlawful if police see at least three people engaged in "disorderly conduct," Walczak said.

The Pittsburgh summit brought thousands of protesters to Pittsburgh, including anarchists who responded to calls to disperse by rolling trash bins, throwing rocks and breaking windows. Many protesters condemned the harsh law enforcement response that followed, which included pepper spray canisters, rubber bullets, flash-bang grenades and huge speakers emitting earsplittingly loud sirens.

One of the plaintiffs, Jason Munley, 31, of Pittsburgh, said he wasn't part of the Pitt protest but stopped to give police "the middle finger" on his way to a friend's house. Munley said he did that because he disagreed with police tactics at the G-20, and was shot with pepper spray pellets and arrested.

Ben Tabas, 20, was a Pitt student who was recording the protest on video. He said he tried to disperse but was hemmed in by police and arrested. He told officers he was a diabetic, but wasn't allowed to access his medication and in jail was given a type of insulin not prescribed by his doctor.

Casey Brander, a 21-year-old student at nearby Carnegie Mellon University, walked over with a friend to check out the protest and a concert before it. Brander said she tried to leave but kept being turned back by police in riot gear.

"The police didn't say anything, they just marched and beat their shields and had this very intimidating presence," Brander said.

One officer called her his "girlfriend" and other officers told some women being arrested that they were "hot" said Brander, who was held for 19 hours.

Trying to avoid arrest, she and her friend actually called 911 for help getting out of the plaza.

"It just seemed like the thing to do when you're cornered; it's what I was taught to do since I was young," she said.