Police arrested dozens of Occupy Wall Street protesters on Saturday night during a protest marking the movement's six-month anniversary at its birthplace in New York's Zuccotti Park.
The sweep of the park by police just before midnight capped a day of demonstrations and marching in lower Manhattan. There was no official word on the number of arrests but dozens of people were handcuffed and led out of the park.
Earlier in the day, 15 people were arrested and three officers suffered injuries, police said.
Protesters reconvened at the park following afternoon marches through New York's financial district. By 11pm roughly 300 had gathered there.
"This is our spring offensive," said Michael Premo, 30, of New York, who identified himself as a spokesman for the movement. "People think the Occupy movement has gone away. It's important for people to see we're back."
Inspired by the pro-democracy Arab Spring, the Wall Street protesters targeted US financial policies they blamed for the yawning income gap between rich and poor in the country, between what they called the 1 percent and the 99 percent. The demonstrators set up camp in Zuccotti Park on Sept. 17 and sparked a wave of protests across the United States.
On Saturday evening, several dozen police ringed the park and watched the crowd. Detective Brian Sessa said no action would be taken as long as the activists made no move to establish a camp.
Shortly after 11.30pm, some protesters began to erect tents near the center of the park and police began to move in, according to protester Cari Machet.
"They came in to shut it down," Machet said. "They told us we had to leave because the park was closed."
When about 100 officers entered the park, dozens of protesters sat on the ground and refused orders to leave. They were then carried out in plastic handcuffs and put in police buses and vans.
The park was cleared within 20 minutes, and by midnight no protesters remained in its boundaries.
Anniversary games of cat and mouse
Events got under way near midday on Saturday, with street theater troupes performing and guitar players leading sing-alongs. Some boisterous protesters marched through the streets of the financial district, chanting "bankers are gangsters" and cursing at police.
As they have in past marches, protesters led police on a series of cat-and-mouse chases. Marchers at the front of the crowd would suddenly turn down narrow side streets, startling tourists and forcing police to send officers on motor scooters to contain the crowd.
The movement has made headlines for its clashes with police after campsites were set up for months in cities from New York to California. The camps were eventually shut down by authorities citing zoning regulations and public health concerns.
In New York, the Occupy movement lost significant momentum in November when a pre-dawn sweep broke up the encampment at Zuccotti, although Occupy protests in Oakland, California, in January led to police firing tear gas into crowds of protesters and more than 200 were arrested.
Protester Paul Sylvester, 24, of Massachusetts said he was "thrilled" to be back at the park but said he hoped the movement would begin to crystallize around specific goals.
"We need to be more concrete and specific," he said.
Critics say the Occupy movement lacks direction and clear demands.
It continues to draw celebrities, however. On Saturday night, independent filmmaker Michael Moore strode through the park before the police incursion.
"I think it's great that this movement continues to grow," Moore said. "I think the goals are clear. People are concerned that they have no control over their own democracy. They have no control over their own lives.
"This is the beginning. This park is sacred ground for millions across the country."