Occupy Wall Street protesters have been barred from bringing tents and camping gear back into Manhattan's Zuccotti Park, following an early-morning police crackdown at the movement's origin that also played out in cities across North America.

Despite the ruling, which could be a major blow to the two-month-old protest movement, organizers said that they will continue their demonstration. They also mulled a change of location.

"This is much bigger than a square plaza in downtown Manhattan," said Hans Shan, an organizer who was working with churches to find places for protesters to sleep. "You can't evict an idea whose time has come."

New York Supreme Court Justice Michael Stallman said that while the protesters are entitled to free speech, that right doesn't mean they can camp indefinitely in the privately owned park.

Earlier, hundreds of police officers showed up at the park at about 1 a.m. Tuesday and informed the Occupy protesters that they had to leave so that sanitation workers could clean the park grounds.

The notices given to protesters said the Zuccotti Park encampment posed "an increasing health and fire safety hazard to those camped in the park, the city's first responders and the surrounding community."

The protesters were told that they would be able to return within hours, but would only be allowed to take one small bag. Items not permitted included sleeping bags, tents or tarps.

Two by two, police began letting protesters back in when officials received word that the National Lawyers Guild had received a temporary restraining order allowing the protesters to return with their tents.

Mayor Michael Bloomberg told reporters at a morning press conference that it was necessary to clear the protesters from the park because their encampment was prohibiting others from accessing and enjoying a public space.

Bloomberg said the people who had spent the past two months in the park had a right to air their views in public. But they didn't have the right to keep others from doing the same.

"No right is absolute and with every right comes responsibility," Bloomberg said.

"The First Amendment gives every New Yorker the right to speak out. But it does not give anyone the right to sleep in a park, or otherwise take it over, to the exclusion of others. Nor does it permit anyone in our society to live outside the law."

Bloomberg said there were also health and safety concerns at the protest site, which prompted the need for a clean-up.

Police initially reported that at least 70 protesters had been arrested at Zuccotti Park overnight, though Bloomberg said as many as 200 arrests occurred in the area overnight.

"Keep in mind, it's still early and some arrests occurred off the site, as opposed to on the site, so it's a question of definition," said Bloomberg.

Bloomberg said the police action was taken overnight "to reduce the risk of confrontation in the park, and to minimize disruption to the surrounding neighbourhood."

Overnight, the protesters were warned that any property left behind would be removed. But Bloomberg said that they will be able to retrieve any of their missing belongings.

On Tuesday, protesters like Shan said that the crackdown could actually help the movement grow.

"People are really recognizing that we need to build a movement here," Shan told The Associated Press. "What we're dedicated to is not just about occupying space. That's a tactic."

Meanwhile, police action against protests in other cities prompted lawsuits from the American Civil Liberties Union.

In Nashville, Oakland, Calif., and Trenton, N.J., protesters won partial victories when temporary restraining orders were issued.

"There is no such thing as a beginning, middle and end to free speech rights," said ACLU chief Anthony Romero. "The right ... doesn't toll after a certain time period."