Scores of protesters were arrested in Manhattan Saturday as a march against social inequality turned violent.

Hundreds of people carrying banners and chanting "shame, shame" walked between Zuccotti Park, near Wall St., and Union Square calling for changes to a financial system they say unjustly benefits the rich and harms the poor.

At least 80 people were carted away in police vehicles and up to five were hit with pepper spray near 12th St. and Fifth Ave., where tensions became especially high, police and organizers said.

The National Lawyer's Guild, which is providing legal assistance to the protesters, put the number of arrests at 100.

Witnesses said they saw three stunned women collapse on the ground screaming after they were sprayed in the face.

A video posted on YouTube and NYDailyNews.com shows uniformed officers had corralled the women using orange nets when two supervisors made a beeline for the women, and at least one suddenly sprayed the women before turning and quickly walking away.

Footage of other police altercations also circulated online, but it was unclear what caused the dramatic mood shift in an otherwise peaceful demonstration.

"I saw a girl get slammed on the ground. I turned around and started screaming," said Chelsea Elliott, 25, from Greenpoint, Brooklyn, who said she was sprayed. "I turned around and a cop was coming ... we were on the sidewalk and we weren't doing anything illegal."

Police said 80 protesters were arrested or ticketed at multiple locations for disorderly conduct, blocking traffic and failure to obey a lawful order but the number could rise.

Officials said protesters did not have a permit for the march and one demonstrator was charged with assaulting a police officer, causing a shoulder injury. The NYPD was investigating the use of pepper spray.

"I was shocked because it seemed like one person after another was being brutally tackled, and it wasn't clear why," said Meaghan Linick, 23, from Greenpoint, Brooklyn, who attended the rally. "I was deeply disturbed to see them throw a man [down] and immediately they were pounding on him. Their arms were going back in the air. I couldn't believe how violent five people needed to be against one unarmed man."

The protesters, joined together under the banner of an organization called Occupy Wall Street, have been stationed in Zuccotti Park since last weekend, attempting to draw attention to what they believe is a dysfunctional economic system that unfairly benefits corporations and the mega-rich.

"The central message is that in this country, there needs to be more conversation about wealth and power," said 23-year-old student Patrick Bruner.

As night fell, those detained were hauled out of vans and buses and into police precincts to be processed.

Hundreds more protesters congregated in Zuccotti Park where for a while another clash with police seemed imminent, but as midnight approached tension eased as die-hards prepared to camp out for the night.

With Ashley N. Fleming