NEW YORK (CNN) -- Police encircled Lower Manhattan's Zuccotti Park on Sunday as protesters geared up to observe the one-year anniversary of Occupy Wall Street.

A loosely organized group of demonstrators first gathered in New York one year ago Monday as part of a movement that thrust "the 99 percent" into the political lexicon. The protests spread to dozens of cities across the United States.



By 7 p.m. Sunday, New York police said there had been no arrests during the day -- but they put the number of arrests Saturday at about 40. Protesters faced various charges including disorderly conduct, resisting arrests and felony assault.

Video of the scene showed people near the park being detained, while others banged on drums and shouted. Zuccotti Park is located in the city's financial district.

The group's messages have ranged from protecting the environment to protests over education costs. There's been an overriding theme of condemning income inequality and social injustice.

It put out a statement Sunday, saying "the day's events are about flexing people power in the streets and utilizing public spaces."

"The Occupy movement continues to utilize culturally creative tactics to build the movement for social and economic justice," the group said.

The movement also has been criticized for its lack of focus, and over reliance on a physical space.

"The camp is one of the central points for the first couple of months and that's just not a sustainable form of protest," said Fordham University professor Heather Gautney, referring to Zuccotti Park.

"So I think there was a transition into more localized acts of protest but they never really had the momentum that the camps had."

Occupy had "a problem of transitioning into a new strategy," she said.

The group's mantra has traditionally been directed against the so-called privileged 1 percent of society -- such as banks, the mortgage industry, insurance providers and others.

The 99 percent is a reference to the broader public, which the group said had been undermined by those institutions.