A crowd of anarchists pummeled and kicked a police officer yesterday, leaving him conscious but bloody on the pavement on Eighth Avenue at the tail end of an impromptu protest march. The attack may foreshadow anarchists’ plans for today.

Police are still investigating, but the deputy police commissioner for public information, Paul Browne, said that around 8 p.m. a female officer radioed for assistance when “hard core types” surrounded her on 29th Street and Eighth Avenue. Uniformed officers went to her aid and encircled her, but the anarchists picked up metal barricades and began throwing them at police, Mr. Browne said.

Plainclothes officers on scooters rode into the scene through a gap in the barricades set up on 29th Street, and, according to witnesses, began bumping people in the crowd with their wheels of their scooters in an effort to disperse the mob. One of the officers was knocked off his bike to the pavement, and the pro testers went after him, punching and kicking him, Mr. Browne said.

“We got all the way to this point when a group of these hard-core types broke out and started this melee,” Mr. Browne said. “There was a group of these anarchist types moving in and taking control.”

He described the attackers as wearing goggles and bandanas and said they commonly take over the end of events that had been peaceful.

Organizers of the march and rally that preceded it, The Economic Human Rights Campaign, refused to comment on the incident other than to say it occurred as the march was ending and many of the participants had gone home.

Eleven arrests today brought the total number of protesters arrested since Thursday to 560.In earlier protests, one police officer suffered a third-degree burn when protesters set fire to a papier-mache dragon and another required 38 stitches when he was injured while chasing protesters at the Plaza Hotel.

A loosely organized group of anarchists called the “A31 Coalition” has vowed not to harm anyone in today’s “direct actions,” but the group has never said it would not damage property. The group said in a press release that there would be “spontaneous protests and street theater” throughout the day, with locations focused on Madison Square Garden, CNN’s Midtown headquarters, Fox News’s Mid town headquarters, and three delegate hotels: InterContinental The Barclay New York, Hilton Times Square, and Millennium Broadway. On Wednesday, 5,000 protesters holding pink slips will line sidewalks from Wall Street to the garden to symbolize unemployed Americans.

All of the events scheduled will be attended by observers from the National Lawyer’s Guild, identifiable in their neon green hats. The group offers pro bono legal assistance for protesters arrested during the protests. Yesterday members of the guild announced that some of their observers have been arrested along with protesters.

A guild spokeswoman, Shonna Carter, said that seven or eight of the group’s observers were arrested while watching protests on Sunday at the United for Peace and Justice march through Manhattan. The observers were targeted by police, Guild members claimed. They released a statement: “The National Lawyer’s Guild is urging the New York Police Department to immediately stop targeting Guild legal observers.”

One observer, Keith Emmer, a nonguild attorney, said he was arrested at about noon at Sixth Avenue between 33rd and 34th streets as he was pedaling in a group of bicycle protesters.

“The legal observers were there to simply watch the protest and document any arrests, document any police action,” said Mr. Emmer. “It seemed clear that the police were actually targeting the legal observers. For them it was a way of intimidating and establishing control.”

Mr. Emmer described the way he was arrested: “They knocked into me with a moped and told me I was being arrested.”

In a press release, the guild claimed that observers had been arrested, harassed, and even assaulted by police.

“One legal observer was grabbed from behind by the police while he was on a bicycle, thrown to the ground and arrested. An arresting officer was heard to state, ‘We got one of their captains,'” the release said.

Mr. Emmer said he was initially taken to a “Guantanamo Bay-style holding pen” off the West Side Highway for several hours, and then he was taken to The Tombs. Mr. Emmer said he still doesn’t know what he was charged with.

In response to the guild’s complaints, Mr. Browne of the Police Department published a statement: “Police officers have been restrained and professional throughout. The single largest factor in delaying the release of arrested demonstrators is their refusal to identify themselves. Persons arrested are also given opportunities to make telephone calls.”

Four people were arrested at the “March For Our Lives” yesterday, two for disorderly conduct and two in the assault on the officer.

The march began as a permitted rally on Dag Hammarskjold Plaza on First Avenue and 47th Street in front of the United Nations building. Turnout was sparse at first, but as the rally ran on, protesters from an earlier, permitted march, organized by “Still we Rise,” began to stream in from across town. By the time the final speaker was declaring “God is on our side” protesters had filled the plaza, overflowed into a nearby cafe, where many rested and drank beer, and into the nearby Katherine Hepburn Garden. Police officers in riot gear lined 47th Street and a reserve force of 40 officers stood in formation a block away on Second Avenue.

Nearly all the protesters were prepared to be arrested.

“I would rather spend billions to rebuild schools,” said a marcher, Allen Goldman, from Brooklyn. “I’ll exercise my democratic right to be able to demonstrate on the streets of my city.”

At the moment of confrontation, organizers sent a vanguard of four parents, pushing two infants in strollers ahead of them, followed by a contingent of deaf protesters, and the police let them through. Police officers from the deputy commissioner of public information’s office plowed a path ahead. At Second Avenue, the march turned south, drums pounding, banners waving, with a cordon of bicycle- and moped-mounted police officers dividing the avenue in half.

“It’s a great march, so peaceful,” said a marcher from Houston, Chris Meyer, before the assault on the officer. “The police officers in New York are pretty good. In Houston this would never have happened.”

Police have refused to comment on who made the decision to let the protesters march, or why.