Police in riot gear closed in before dawn Monday on anti-Wall Street activists who defied a midnight deadline to vacate an 8-week-old encampment outside Los Angeles City Hall, but the police later pulled back.

After a tense standoff with protesters who had taken over a downtown intersection, police reopened the streets in time for morning rush-hour commuters, but a crowd of activists estimated to have numbered at least 2,000 overnight remained at City Hall, for the time being.

Four demonstrators were arrested on suspicion of being present at an unlawful assembly during the brief confrontation, and police withdrew from the immediate vicinity of the City Hall park a short time later.

Mayor Antonio Villaraigosa had given protesters until 12:01 a.m. local time to dismantle their tents and clear out of the park or face a forcible removal, setting the stage for the latest showdown between leaders of a major U.S. city and the Occupy Wall Street movement.

But about two hours after the eviction deadline had passed, police commanders said they would permit the Occupy LA encampment to stay until at least daybreak. Police Commander Andrew Smith later said he thought it highly unlikely that the camp would be forced to shut down on Monday.

Across the country, a 5 p.m. Sunday deadline set by Philadelphia officials for Occupy protesters there to move from one municipal plaza to came and went without incident.

Dozens of people heeded the order but many tents and other structures stayed put. Police sources said authorities are hoping the rest of the protesters will relocate voluntarily and that no major actions are expected before Tuesday.

SUPPORTERS RALLY TO BOLSTER CAMP

The Los Angeles encampment is among the largest on the West Coast aligned with a 2-month-old national Occupy Wall Street movement protesting economic inequality, high unemployment and excesses of the U.S. financial system.

Staking its place since October 1 on the grounds surrounding City Hall, the compound grew in size to roughly 400 tents and 700 to 800 people, organizers and municipal officials said. At least a third are believed to be homeless.

By Sunday night the size of the crowd outside City Hall swelled as supporters from organized labor, clergy, civil rights and other groups streamed into the area, answering a call for an 11th-hour show of support for the campers.

The overall number of protesters, some wearing gas masks, had grown to at least 2,000 by late Sunday, police estimated.

After keeping out of sight throughout the day on Sunday, police began to make their presence known as the mayor's eviction deadline came and went, and the protesters' mood turned from calm and festive to rowdy.

Demonstrators and police confronted each other overnight but except for some debris thrown by protesters at one point, there was no violence. One skirmish involved an intersection occupied by protesters.

Minutes after ordering protesters in the street to disperse, dozens of helmeted police carrying night sticks and special shotguns for firing bean-bag projectiles enclosed the intersection and forced their way into the crowd.

Most in the crowd quickly retreated into the park, as onlookers chanted Whose street? Our Street at police and shouted at those defying police to Get off the street!

Someone hurled what appeared to be pieces of a bamboo pole and a bottle at police, and Smith said four arrests were made.

Los Angeles has been relatively accommodating to its Occupy group compared to other major cities, with Villaraigosa at one point providing ponchos to campers when it rained.

But after the collapse of negotiations aimed at persuading protesters to relocate voluntarily, the mayor said last week the encampment would have to go.

In a statement released Sunday evening, the mayor complimented the protesters for staying peaceful. But, he added, It is time for Occupy LA to move from focusing their efforts to hold a particular patch of park land to spreading the message of economic justice and restoration of balance to American society.

He said he hoped to avoid the sporadic violence that erupted in other cities when police used force against Occupy protesters.

A number of protesters early Monday credited the police with showing restraint, including Clark Davis, an Occupy LA organizer, who said to Smith and a group of other officers standing by, You guys have been fantastic.