Hundreds of riot police flooded into downtown Los Angeles and Philadelphia early Wednesday to clear anti-Wall Street protest camps in mostly peaceful operations that saw dozens arrested.

The latest moves targeting the two-month-old protest movement against corporate greed and inequality came days after announced eviction deadlines and did not bring the running clashes and tear gas that have marked previous raids.

In Los Angeles, dozens of officers in helmets formed lines to seal off an area around the City Hall park camp, while others began arresting around a dozen protesters and leading them away in plastic handcuffs.

Police announced over loudspeakers that they were declaring an unlawful assembly shortly after midnight (0800 GMT Wednesday), calling on people to leave the area "immediately" or face arrest and possible other action.

After a couple of hours of anticipation about where the police would come from, a mass of helmeted LAPD officers burst out of the City Hall doors while others began arresting people on the lawn outside.

But after the initial burst of action the calm returned, as police gently pushed the crowds out of the central protest area and began arresting a stream of people and dismantling tents.

By 2:00 am (1000 GMT) the situation appeared to be completely under control.

"It went as well as we could have expected," LAPD chief Charlie Beck was quoted as saying by the LA Times.

The CNS news agency earlier said that rubber bullets had been fired during the initial confrontation, but later dropped the report.

The operation got under way two days after a midnight Sunday (0800 GMT Monday) deadline set by LA Mayor Antonio Villaraigosa to clear the camp, which has been in place since October 1.

"We have taken a measured approach to enforcing the park closure because we have wanted to give people every opportunity to leave peacefully," the mayor said in a statement Wednesday.

"Once the park is cleared, it will be repaired and returned to all Angelenos to exercise their First Amendment rights," he added, referring to the US constitutional guarantee of freedom of speech and assembly.

Hundreds of protesters—up to 500 according to one estimate—had been congregating in the area when the police action began, according to an AFP photographer on the scene.

Earlier some 30 buses carrying riot police arrived from a staging area at Dodgers' Stadium, a few miles from City Hall. Officials said some 1,200 officers overall were involved in the operation.

At around the same time as the Los Angeles operation, riot police converged on a similar Occupy Wall Street camp in the eastern city of Philadelphia, clearing a tent camp and setting off an hours-long march through downtown.

The police, many mounted on bicycles, initially flanked the group of some 50 marchers, but as rush hour approached they cornered the protesters in a side street and arrested around half of them, an AFP reporter said.

"I think our officers showed a lot of restraint. We've been very patient," Philadelphia Police Commissioner Charles Ramsey told AFP.

In both cities the police were followed by garbage trucks, which carted off the tents, tarps and signs that had accumulated in the camps.

Minor scuffles broke out in both police raids, but the scene was far calmer than in previous raids, including one in Oakland, California last month in which police fired tear gas and clashed with demonstrators.

In both cities, protesters had been warned to evacuate and given a Sunday deadline to leave the parks where they had been camped out for two months.

The Occupy Wall Street movement started in September as a ragtag march on New York's Financial District and has since grown into a national movement centered on tent camps in New York, Washington and other major cities.

The loosely organized, left-leaning protesters insist they are exercising their freedom of speech in the run-up to November 2012 national elections.

But local authorities have said the tent camps—which activists often share with the homeless—threaten public health and safety.

New York police cleared the tent camp in Manhattan's Zuccotti Park—the epicenter of the Occupy Wall Street movement—earlier this month.