Helicopters hovered, shining spotlights on a downtown Atlanta park where police either led away or arrested dozens of Occupy Wall Street protesters who had set up an encampment for about two weeks.

Streets were barricaded around Woodruff Park where as in many American cities protesters have camped out to rally against what they see as corporate greed and a wide range of other economic issues. Before police marched in, protesters were warned a couple of times around midnight to vacate the park or risk arrest.

Organizers had instructed participants to be peaceful if arrests came, and most were.

Police included SWAT teams in riot gear, dozens of officers on motorcycles and several on horseback.

Mayor Kasim Reed on Monday said he planned to revoke the permit allowing Occupy Atlanta protesters to live in the park, but was vague about when that might come.

Late Tuesday, police started surrounding the park at a busy intersection, and some protesters gathered up their tents, pillows, sleeping bags and other belongings, saying they didn’t want to lose them. Right after the order to leave, some did, standing outside the barricades.

Mr. Reed said he was upset over an advertised hip-hop concert that he said drew 600 people to the park over the weekend but didn’t have a permit and didn’t have security guards to work the crowd.

He called the concert “the height of irresponsibility.”

As police moved in, protesters chanted, “Who’s park, our park,” and “We are here, we are stronger, we can’t take it any longer.”

TV images showed the number of police far outnumbering the protesters, who were handcuffed with plastic twist ties and led away to waiting buses.

The arrests in Atlanta appeared peaceful. In Oakland, police shot tear gas in response to rock throwing from some of the demonstrators who had gathered there, authorities said.