Police and activists have clashed at a park in New York where hundreds of people had gathered to mark six months since the beginning of the city's Occupy Wall Street protests.

The clashes, late on Saturday, came as some activists attempted to re-occupy Zuccotti Park, which police had earlier declared closed for the evening.

The Manhattan park, close to Wall Street, was where the anti-corporate greed protest movement began in September last year. Activists spent months camping at the site, prompting similar demonstrations in other US cities and abroad.

Police began making arrests after several hundred protesters had remained there, with some erecting a makeshift tent of cardboard and tarpaulin in contravention of rules banning shelters in the park.

More than 100 police officers pushed through the park, clashing with protesters who attempted to stand their ground, The Associated Press news agency reported.

The Reuters news agency reported that dozens of protesters had been led away in handcuffs, although there has been no official word on the number of arrests.

Earlier in the day, hundreds of protesters had marched on nearby Wall Street, resulting in another unspecified number of arrests, police said.

Organizers vowed that Saturday's rally was the first of several events planned to protest against perceived economic injustice.

'We are going to take it back'

One of the activists taking part in the gathering said he hoped the park would again become a home for protesters, in defiance of a police ban on sleeping there which led to the eviction of the protest camp's occupants after two months.

"They're hoping we'll all go away because it's cold," said Rob, 28, declining to give his last name. "The park's become the symbol both for us and for them. We are going to take it back."

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 demands and direction and has lost momentum.

But warmer spring weather in the US has brought expectations that Occupy leaders will try to regain their momentum.

Protesters seemed invigorated by their relatively large numbers compared to the small turnouts during street demonstrations over the winter.

At the park on Saturday, street theatre troupes performed and guitar players led sing-alongs. Some protesters marched through the streets of the financial district, chanting "bankers are gangsters" and cursing at police.

Liesbeth Rapp, 27, who was performing street theatre about economic injustice, said protesters were ready to make some changes.

"I think we've learned a lot about being strategically and tactically smarter," she said. "We're learning to decentralize, and to work in smaller groups."

PHOTO CAPTION
Members of the Occupy Wall St movement are arrested by NYPD officers after protesting at Zuccotti park in New York March 17, 2012

Aljazeera