By Laird Harrison

OAKLAND, Calif., Feb 1 (Reuters) - When anti-Wall Street protesters set out to take over Oakland's shuttered convention center on Saturday, they left no doubt about the reception they expected. Scores concealed their faces with bandanas, and dozens carried shields, some painted with anarchist symbols.

What happened next -- a 10-hour street battle in which demonstrators and police pelted each other with tear gas canisters, smoke grenades and other projectiles -- has intensified a debate within the Occupy Wall Street movement over what forms of confrontation it should embrace.

Activists calling for greater equality in income and tighter regulation of financial institutions have clashed with police across the country since September, usually while advocating non-violence. But a series of conflicts with police in Oakland have stood out as the most violent, with one activist, Iraq war veteran Scott Olsen, suffering a brain injury on Oct. 25.

Protesters on Saturday said they were trying to establish a new headquarters and community center to take the place of the tent camp police dismantled at Frank Ogawa Plaza in front of City Hall last fall. Police lined up on street corners and in front of the convention center to thwart the would-be occupiers.

Objects began flying through the air as soon as demonstrators tore down a section of chain-link fence in front of the building.

"Of all the (anti-Wall Street) marches and rallies in the city of Oakland, this has been the most violent and hostile to the police," said Oakland Police Department spokeswoman Johnna Watson.

Some 400 protesters were arrested, and several police officers and demonstrators were injured.

"While we respect every citizen's right to protest peacefully, we will not tolerate individuals who come to Oakland with an organized strategy to riot, clash with police officers, vandalize property and wreak havoc upon the city," Alameda County District Attorney Nancy O'Malley said in a statement.

Demonstrators accused the police of beating them with batons and of trapping them between police lines, then arresting them for supposedly disobeying orders to disperse.

People in the San Francisco Bay Area appeared to be turned off by Occupy's tactics on Saturday, according to an opinion poll by SurveyUSA.

Of 500 people surveyed on Sunday, 26 percent said they had once supported the Occupy movement and now do not. Added to 31 percent who said they always opposed the movement, the poll suggests a majority of public opinion opposes the group.

Some leaders within the movement were distancing themselves from tactics employed by fellow occupiers on Saturday.

"A lot of conversation is coming out of that, a lot of self-reflection," said Nichola Torbett, a self-described devout Christian who took part in the first Occupy Oakland organizing meetings in September.

Torbett said she has participated in nearly every major Occupy Oakland event and was arrested when police cleared out a protest encampment on Nov. 15. But she stayed away from the march on Saturday.

"It was organized by a very militant anarchist segment of the movement," she said. "I support the idea of taking a building, especially for housing those who don't have housing. But I don't support it with the kind of triumphal attitude I saw expressed."

In November, following a day of mostly peaceful Occupy Oakland rallies that gave way to a night of unrest and over 100 arrests, some activists joined city officials in blaming small bands of agitators who they said provoked police.

Mike King, an organizer of the movement's effort to shut down West Coast ports on Dec. 12, stayed away on Saturday because of "personal obligations."

He defended the demonstrators' attempt to take over a building but said he prefers to devote his energy to building relationships with labor leaders.

Without condemning the attempt to occupy the convention center, labor leaders kept a low profile during the demonstration and its aftermath.

Representatives for the Service Employees International Union, which helped organize Occupy rallies in a number of cities, did not return repeated calls seeking comment, nor did the Alameda Labor Council nor the California Teachers Association.

The California Nurses Association, which has staffed medical stations during previous Occupy Oakland marches, had no official presence at the demonstration Saturday, said spokesman Chuck Idelson. "We don't support violence no matter who is doing it," he said.

Still, many occupiers defend Saturday's action. Shake Anderson, who took part in the march, acknowledged, "it could have been better organized" but insisted the goal was worthy.

City officials are unable or unwilling to help the homeless, hungry and unemployed, he said. Occupy Oakland was meeting those needs in its camp at Frank Ogawa Plaza until it was evicted by the police, he said.

"We need a space so we can feed each other and educate each other," he said. "Let us have our big house and leave us alone." (Editing by Steve Gorman and Daniel Trotta)