OAKLAND (Reuters) - Throngs of anti-Wall Street protesters took over a vacant lot in downtown Oakland on Saturday and began erecting a tent camp to replace one torn down by police, setting the stage for a potential showdown.

Protesters, who have also vowed to set up camp in an adjacent park, marched to the lot and tore down a chain-link fence, pitching tents as a light rain started. Police on the scene did not immediately intervene.

"Occupy Oakland has a new home at 19th and Telegraph," organizers said in a tweet, adding there would be a big "housewarming" party. "Bring tents!"

The move appeared to be a direct challenge to Oakland police who less than a week ago forcibly dismantled a similar protest camp nearby, and risked igniting a confrontation. Police have said they would not allow another encampment.

Previous unrest surrounding protests in Oakland, a West Coast Occupy hot spot, has helped rally support nationwide for the Occupy Wall Street movement launched in New York in September to protest against economic inequality and excesses of the financial system.

The lot and adjacent park are in a rapidly gentrifying area, and protesters said establishing a camp there would be a symbolic move in a city they complained looked out most "for the interests of big business and developers" over ordinary residents.

Oakland police said in a statement it had a "non-confrontational strategy" for preventing a new campsite from being established, but did not elaborate on the details.

"I support the first amendment of the U.S. Constitution and I am a passionate supporter of freedom of speech. However, camping on City property - whether it is in a park or in open space - is illegal and won't be allowed," Mayor Jean Quan said in a statement on Friday.

Police had on Monday evicted protesters from their camp in Frank Ogawa plaza after weeks of indecision over how to deal with the protests, spurred to act after a fatal shooting nearby fueled pressure on the city to close the camp down.

A previous move to remove the camp in October had sparked clashes between protesters and police that wounded a former U.S. Marine and evolved into one of the most violent episodes linked to the Occupy movement.


In a further potential escalation, Oakland protesters announced plans to shut down all West Coast ports on December 12 in coordination with like-minded protesters in Los Angeles.

The Oakland group had briefly forced the closure of the Northern California city's port earlier this month in protests that, while mostly peaceful during the day, turned to clashes at night.

But in a sign of potential fractures in the protest movement, not all march participants agreed on the decision to take over fresh territory.

"This is bigger than occupying a space," said Liz Kimura, a retiree and activist with the Service Employees International Union local 1021 who had been taking part in a protest about educational inequality and budget cuts.

The union organizers would not take part in the attempt to take over the lot and adjacent park, she said.

Across the bay, in San Francisco, city workers cleared out vacant tents amounting to roughly 10 percent of an encampment in that city's Justin Herman Plaza, San Francisco Police Department spokesman Officer Albie Esparza said.

No disturbances or arrests were reported during the move. Esparza said police considered the tent city there illegal, but could not elaborate on specific plans to clear the site.

To the north in Davis, the University of California campus in that city said on Saturday it would launch an investigation over video footage that appeared to show campus police using pepper spray against seated student protesters at close range.

"Yesterday was not a day that would make anyone on our campus proud," UC Davis Chancellor Linda P.B. Katehi wrote in a public statement. "The use of pepper spray as shown on the video is chilling to us all and raises many questions about how best to handle situations like this."

She announced a task force of faculty, students and staff to investigate the incident and said she had also asked the school to reevaluate whether its policy on encampments offered students sufficient "flexibility to express themselves."

(Writing and additional reporting by Mary Slosson; Editing byCynthia Johnston)

Mochila insert follows.