In a tense showdown above New York's East River, the police arrested more than 700 demonstrators from the Occupy Wall Street protests who took to the roadway as they tried to cross the Brooklyn Bridge.
The police said it was the marchers' choice that led to the enforcement action.
Chief spokesman for the New York Police Department, Paul J. Browne, said, ''Protesters who used the Brooklyn Bridge walkway were not arrested.
''Those who took over the Brooklyn-bound roadway and impeded vehicle traffic were arrested.''
But many protesters said they believed the police had tricked them, allowing them on to the bridge, and even escorting them partway across, only to trap them in orange netting after hundreds had entered.
Occupy Wall Street media coordinator Jesse A. Myerson said, ''The cops watched and did nothing, indeed, seemed to guide us on to the roadway.''
He marched but was not arrested.
Things came to a head yesterday as about 1500 marchers reached the foot of the Brooklyn-bound car lanes of the bridge, just east of City Hall.
In their march north from Zuccotti Park in Lower Manhattan - headquarters of the past two weeks of a protest movement against what demonstrators call inequities in the economic system - they had stayed on the sidewalks, forming a long column of humanity penned in by officers on scooters.
Where the entrance to the bridge narrowed their path, some marchers, including organisers, stuck to the generally agreed-upon route and headed up on to the wooden walkway that runs between and about 4.5m above the bridge's traffic lanes.
New York Civil Liberties Union's Christopher T. Dunn said about 20 others headed for the roadway. Some of them chanted, ''Take the bridge!''
They were met by a few police supervisors, who blocked the way and announced repeatedly on bullhorns that if they kept blocking the road, they would be arrested.
There were no physical barriers, though, and at one point, the marchers began walking up the road with police commanders in front of them ? seeming, from a distance, as if they were leading the way.
The chief of department, Joseph J.Esposito, and a horde of other white-shirted commanders were among them.
After allowing the protesters to walk about a third of the way to Brooklyn, the police then cut the marchers off and surrounded them with orange nets on both sides, trapping hundreds of people, Mr Dunn said. Protesters at times chanted, ''White shirts! White shirts!'' And officers began making arrests, at one point plunging briefly into the crowd to grab a man.
The police said the arrested demonstrators were being held at various police stations and that they would be charged, at a minimum, with disorderly conduct. A freelance reporter for The New York Times, Natasha Lennard, was among those arrested. She was later released.
Mr Dunn said that he believed only people at the very front could hear the warning, and he was concerned that those in the back ''would have had no idea that it was not OK to walk on the roadway.''
Mr Browne said that people in the rear who might not have heard the warnings were not arrested and were free to leave.
Resident Etan Ben-Ami, 56, said the police seemed to make a conscious decision to allow the protesters to claim the road. New York Times